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PUBLISHED BY 

JOHN WILEY & SONS. 


Theory and Practice in the Designing of Modern 
Framed Structures. 

Profusely illustrated with figures in the text and 
full-page plate, including many half-tones. 4to, 
cloth, $10.00. 

The Theory and Practice of Surveying. 

Designed for the use of Surveyors and Engineers 
generally, but especially for the use of Students 
in Engineering. 8vo, cloth, $4.00. 

Stadia and Earth=woik Tables. 

Including Four-place Logarithms, Logarithmic 
Traverse Table, Natural Functions, Map Projec¬ 
tions, etc. 8vo, cloth, $1 25. 


















THE LATE PROFESSOR JOHANN BAUSCHINGER 



(See Appendix A.) 


Frontispiece. 











THE 


MATERIALS 



A TREATISE FOR ENGINEERS 

ON Til K 

STRENGTH OF ENGINEERING MATERIALS. 



J. B. JOHNSON, C.E., 


It 

Professor of Civil Engineering in Washington University, St. Louis, Mo. ; Member 
of the Institution of Civil Engineers ; Member of the American Society of 
Civil Engineers: Member of the American Society of Mechanical 
Engineers ; Corresponding Member of the American Insti¬ 
tute of Architects ; Member of the International 
Association for the Standardizing of 
Methods of Testing Materials; 
etc , etc. 



.StCcrvxcl t tA ttr GW 

K'Vlse d cx-a v c.\0 'v.'rA*. k 

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NEW YORK I v, 

•JOHN WILEY & SONS. 
Lonhon: CHAPMAN Ar HALL, Limited. 



ISAS' 



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PREFACE, 


The rational designing of any kind of construction involves a knowledge 

of— 

The external forces to be resisted, transformed, or transmitted; 

The internal stresses resulting therefrom; 

The mechanical properties of the materials to be employed to accomplish 
the objects sought. 

Of these three coordinate departments of knowledge the first two are 
founded on the sciences of mathematics and applied mechanics. The last 
one, however, does not rest on any deductive science, as this information 
can only be gained by patient, expensive, and competent research. For 
this reason the third essential named above has not kept pace with the other 
two kinds of engineering science; but, on the other hand, it furnishes very 
much greater rewards to the skilled investigator. 

During the past twentyffive years the number of such investigators has 
increased from a scattering few to hundreds and even thousands, and these 
are now found in all enlightened nations. The results of their original 
studies and experiments are pouring in upon us from all countries, in many 
languages; and no practising engineer can hope to even scan, much less to 
appropriate and assimilate, more than a very small part of this vast wealth of 
experimental knowledge.* In the following work the author presents to his 
readers a condensed and concise summary of such portions of the knowledge 
now available on this subject as he has found suitable for such a work. He 
is fully aware of its incompleteness and of its more or less fragmentary 
character. Yet with all its faults he believes it contains sufficient reliable 
information, not commonly accessible elsewhere, to justify its publication in 
this form. 


* The author has one list of original contributions to the subject of the Strength of 
Materials filling 140 quarto pages. 


ill 




IV 


PREFACE. 


When the work is used as a text-book in schools of engineering the 
instructor would do well to assign only such portions of Part I as are required 
to supplement the student's course in applied mechanics; to have his students 
read Part II if they do not get this information in other ways; to dwell 
longer and with more care on Part III; and to call attention only to such 
portions of Part IY as pertains to the particular course the students are 
taking. In this way the book may be made intelligent and familiar to the 
student, and so become to him a great and lasting aid in designing, testing, 
and inspecting, without requiring more time than can be devoted to the 
subject. This course should precede or accompany an experimental course 
in the testing laboratory, with which all American schools of engineering 
are now equipped. 

An unusual use has been made of stress-diagrams and other forms of 
graphical representation of facts and laws, no pains or expense having been 
spared in this direction. So far as possible tables have been omitted and the 
original tabular data have been incorporated in diagrams. A law of relation¬ 
ship cannot he perceived from data arranged in a tabular form. When 
plotted to significant arguments the law not only becomes evident at a 
glance, but when once impressed on the mind through the sense of sight it 
cannot well be forgotten. To obtain this lasting benefit, however, the 
diagram must be intelligently read and understood. The reader is urged, 
therefore, to give great care to the study of all the diagrams which accom¬ 
pany the text on any subject, for, as a rule, the facts, laws, and conclusions 
to he drawn from them are not fully expressed in the text. The diagrams 
must be considered as a part of the text, and they should be read with even 
greater care than is bestowed on the word-embodied ideas. 

Throughout the book, with few exceptions, both in the diagrams and in 
the text, the English units of weight and measure (pound and inch) have 
been employed. The author is of the opinion that until the metric system 
has been definitely adopted it is best to use the old units, and that a double 
system of units is confusing. The revising of books to put them in harmony 
with the decimal system will be but a very small part of the total expense 
entailed by the formal adoption of that system by our Government. As a 
very large part of the data given in the diagrams comes from Continental 
sources, all of which were expressed in the metric system, a great amount of 
labor was required to bring this material into the English system of units. 
Even the results obtained from English sources were generally expressed in 
long tons per square inch, so that this also required reduction to bring it to 
pounds per square inch. 

Some of the author’s usages may be regarded as unwarranted innova¬ 
tions. Especially may this be the case in the matter of the new elastic limit, 
which he proposes for general adoption, and which is discussed in Arts. 13, 
261, 262, and 263. The author bespeaks for these articles a careful consid¬ 
eration and also a study of the many stress-diagrams scattered through the 
book, before his views are condemned. The fact is, something must be done 


PREFACE. 


V 


in this matter, as now no one knows what is meant by “ elastic limit ” with¬ 
out an explanation—which explanation is not usually given. 

The relatively large space given to the subject of timber is not more than 
its importance as a structural material, and the general absence of scientific 
information on the subject would seem to demand. Probably the reason 
little has been given on this subject hitherto, in such works as this, is because 
little has been known. Until the Forestry Division of the U. S. Agricul¬ 
tural Department began the systematic study of timber and timber-trees, 
some five or six years ago, very little accurate or scientific information was 
obtainable as to the mechanical and other properties of American timber. 
The author’s intimate connection with these investigations is a further reason 
why he should here present an adequate account of the work done to date.* 

It has been no part of the author’s aim to give working rules for using 
materials in structures of various kinds, or to propose original specifications 
to be used in the purchase of materials. He has tried to impart a knowl¬ 
edge of the properties of materials; on what these depend; the ordinary 
causes of variation and defects, and how these should be discovered; thus 
making the reader competent to draw his own specifications and to make his 
own rules. 

The latest forms of investigation of metals and building-stones by means 
of the microscope are briefly treated (the former in Appendix B); and a 
chapter has been given on the magnetic properties of iron and steel, and the 
methods to be employed in determining these. 

The author has acknowledged his sources of information in the text, and 
especially in the legends accompanying the cuts. In addition to these he 
desires to make a special acknowledgment here of his obligation to Pro¬ 
fessors Bauschinger, Tetmajer, and Martens; to the French Commission 
Report; and to Mr. Henry M. Howe, Prof. Thomas Turner, Mr. G. R. 
Redgrave, Prof. J. 0. Arnold, Mr. Thos. Andrews, Mr. H. H. Campbell, and 
to Dr. B. E. Fernow. His thanks are also due to Dr. Wm. Trelease for 
assistance in obtaining illustrations of American trees in Chap. XIII; to 
Mr. II. A. Wheeler, E.M., for the chapter on the manufacture of paving- 
brick; to Mr. W. A. Layman, M.S., for the chapter on the magnetic prop¬ 
erties of iron and steel; and to Prof. H. Aug. Hunicke, E.M., for revising 
the manuscript of Chapters VII to XI inclusive. 

There are to-day a few exceptionally fertile sources of exact information, 
on subjects pertaining to the materials of construction, prominent among 
which may be named : 

1. The annual publications of the Results of Tests made at the U. S. 
Arsenal, Watertown, Mass., beginning in 1882. 

2. Bauschinger’s Communications from the Laboratory of the Technical 
School at Munich, Germany. 

3. Tetmajer’s Communications from the Laboratory of the Federal Poly¬ 
technic School, Zuric h, Switzerland. __ 

* The author has had entire charge of the mechanical tests, some 40,000 of which 
liave been made in his laboratory at 8t. Louis. 






T i PREFACE. 

4. Martens’ Communications from the Laboratory of the University of 
Berlin, Germany. 

5. The Report of the French Commission (of 115 members) on the 
Standardization of Tests of the Materials of Construction, in four quarto 
volumes, 1895. 

6. The Monthly Journal, Baumaterialenkunde, published in Stuttgart, 
as the organ of the International Society for the Standardization of the 
Tests of Materials of Construction. 

The entire engineering profession is so indebted to the late Prof. Johann 
Bauschinger for the work he has done in developing the scientific testing 
of materials that the author of this work has chosen to express his feeling 
of obligation to him by using his portrait as a frontispiece and giving a 
brief account of his life in Appendix A. 

That this work mav contribute somewhat towards more rational, safe, 

J 

and economic practices in the designing of all kinds of construction has 
been the purpose and is now the hope of 

The Author. 

St. Louis, Mo., Jan. 1897. 


PREFACE TO THE SECOND EDITION. 


Besides receiving a careful and thorough revision throughout, this edi¬ 
tion contains some substantial additions, the more important of which refer 
to Combination Steel and Concrete Beams; Cast-iron Columns; Impact 
Tests; Cement Tests for Fineness; Commercial Analyses of Portland Ce¬ 
ments; Relation between the Crushing and Cross-breaking Strength of Tim¬ 
ber; The Preservation of Timber; Nickel-steel; and The Fatigue of Metals. 

It is the author's purpose to keep this work up to the most advanced 
state of the science of the Materials of Construction, and to do this in a field 
in which new properties are a matter of almost daily discovery requires con¬ 
stant changes and additions. Thus the wonderful and newly discovered 
properties of nickel-steel, first published in France in May, 1898, are in¬ 
cluded in this edition, but could not have been even anticipated in the first 
edition, which is now little more than a year old. The same is true of the 
other new matter in this edition. It is the duty of an author of a technical 
book to collate, classify, and digest all the important knowledge falling 
within the scope of the proposed work which is public property at the time, 
besides including such available new and original matter as has not yet been 
published, and it is the author’s purpose to try to reach this standard of 
utility in each succeeding edition of his several works. This will necessitate 
constant changes and additions, and involves, of necessity, the relative 
depreciation of previous editions. This embarrassment obtains, however, 
with all scientific work, and should not be offered as a criticism of the 
author who follows the practice, as is sometimes done. 

J. B. J. 

St. Louis, Mo., July 1898. 




TABLE OF CONTENTS. 


PART I. 

SYNOPSIS OP THE PRINCIPLES OF MECHANICS UNDER¬ 
LYING THE LAWS OF THE STRENGTH OF 

MA TERIA LS. 


CHAPTER I. 

GENERAL NATURE OF DEFORMATION AND STRESS. 

PAGE 

Elastic and Plastic Bodies—Stress and Deformation—Proportionality of Stress and 
Deformation inside the Elastic Limits—Kinds of Deformation and Stress— 
Longitudinal and Lateral Deformation under Direct Stress—Angular Defor¬ 
mation under Direct Stress—Relation between Shearing and Direct Stresses 
— Shearing Modulus of Elasticity. I 


CHAPTER II. 

MATERIALS UNDER TENSILE STRESS. 

General Phenomena accompanying Tensile Tests—Significant Results of Tensile 
Tests—True Elastic Limit—Apparent Elastic Limit—Ultimate Strength— 
Percentage of Elongation—Reduction of Area of Cross-section. 10 


CHAPTER III. 

MATERIALS UNDER COMPRESSIVE STRESS. 

Two Classes of Engineering Materials—Crushing Strength of Plastic or Viscous } 
Materials—Crushing Strength of Brittle Materials—Relation of Crushing 
Strength tc Shearing Strength—Crushing Strength of Prisms—Relative 
Strength of Prisms and Cubes—Loading on a Portion of Cross-section only— 
General Laws of Crushing Strength—Strength of Columns—Weakening 

Effects of Eccentric Loading . ... 24 

vii 






Vlll 


TABLE OF CONTENTS. 


CHAPTER IV. 

MATERIALS UNDER SHEARING STRESS. 

PAGE 

Two Manifestations of Shearing Stress—Moment of Torsion—Shearing Deforma¬ 
tions. 38 


CHAPTER V. 

MATERIALS UNDER CROSS-BENDING STRESS. 

Historical Sketch—Fundamental Equations of Equilibrium—Moment of Resistance 
and Stress on Extreme Fibre—Resistance of Beams of Various Forms of 
Cross-section—Resistance of Beams beyond their Elastic Limits—Distribution 
of Stress and Position of Neutral Axis at Rupture—Moduli of Rupture in 
Cross-breaking—Distribution of Shearing Stress in a Beam—Wooden Beams 
in Shearing and Cross-bending—Deflection of Beams—General Formulae— 
Various Cases analyzed—Table of Moments, Stresses, and Deflections— 
Deflection from Shearing Forces—Determination of Young’s Modulus of 
Elasticity—Rational Designing of Flitched Beams—Steel and Concrete in 
Combination—Flat Plates computed approximately. 42 


CHAPTER VI. 

% 

THE RESILIENCE OF MATERIALS. 

Resilience defined—Varieties of—A Measure of Shock-resistance—Impact Stresses— 
Resilience Areas in Stress-diagrams—Resilience in Direct Stress—In Cross¬ 
bending—In Torsion—Comparative Table..... 75 


PART II. 

MANUFACTURE AND GENERAL PROPERTIES OF THE 
MATERIALS OF CONSTRUCTION 

CHAPTER VII. 

CAST IRON. 

(General Classification of Iron and Steel—Physical Properties of Cast Iron—Carbon 
in—Silicon in—Remarkable Effects of Silicon—Sulphur, Phosphorus, and 
Manganese in—Grading Pig Iron-Foundry Practice—The Cupola—Remelt¬ 
ing—Moulds—Moulding Sand—Size and Shape—Shrinkage—Mechanical 
Properties—Hardness—Strength in Compression, Tension, and Cross-bending 
—Malleable Cast Irou—Method of Manufacture—Mechanical Properties. 87 






TABLE OF CONTENTS . IX 

CHAPTER VIII. 

WROUGHT IRON. 

Methods of Manufacture—The Puddling Process—Oxidation in Puddling—Muck 
Bars—Reheating and Rolling—Repeated Reheatings—Imperfections in Fin¬ 
ished Product—Mechanical Properties—Crystalline Fracture—Welding— 
Effect of Reduction in the Rolls on the Strength. 11? 

CHAPTER IX. 

STEEL. 

Methods of Manufacture—Crucible Process—Bessemer Process—Open-hearth Proc¬ 
ess—Basic and Acid Processes—Comparison of Bessemer and Open-hearth 
Processes—Molecular Structure of Wrought Iron and Steel—Structure as 
affected by Heat Treatment—Mechanical Qualities of Steel—Commercial 
Classification—Quality as determined by Chemical Composition—Influence 
of Carbon on Iron—Three States of Carbon in Iron—Change in the Carbon 
at a Low Yellow Heat—Hardening and Tempering—Effects of Carbon on 
the Mechanical Qualities—On Tensile Strength—On Ductility—On Compres¬ 
sive Strength—Effects of Silicon—Of Manganese—Manganese Steel—Of 
Sulphur—Iied-shortness—Sulphide of Iron Dangerous—Of Phosphorus—On 
Ductility—On Strength—Hardening—Tempering—Annealing—Corrosion... 133 

CHAPTER X. 

THE MINOR OR AUXILIARY METALS OF CONSTRUCTION AND 

THEIR ALLOYS. 

Copper — Zinc — Tin—Aluminum — Nature of Metallic Alloys—Copper-zinc-tin 
Alloys—The Brasses—The Bronzes—Alloyed Aluminum—Aluminum in 
Steel—Fusible Alloys. 172 


CHAPTER XI. 

LIME, CEMENT, MORTAR, AND CONCRETE. 

Quick, or Fat, Lime—Hardening of Lime-mortar—Hydraulic Lime—Natural 
Cement—Portland Cement—Historical Account of—Ingredients of—The 
Clay—Silica and its Compounds—Alumina—Sulphur Compounds—Chemical 
Reactions in the Furnace—Chemical and Physical Changes in Setting and 
Hardening—Slag-cements—Sources of Raw Materials for Portland Cement- 
Processes used in Pulverizing and Mixing—Processes used in Burning— 
Grinding the Clinker.... 181 


CHAPTER XII. 

THE MANUFACTURE OF VITRIFIED PAVING-BRICK. 


Definition of—Clays employed—Physical Properties of Clays—Preparation of the 

Clays—Moulding—Drying and Burning—Annealing—Sorting. 196 






X 


TABLE OF CONTENTS. 


CHAPTER XIII. 

TIMBER. 

/! • 

Structure and Appearance—Classes of Trees—Sapwood and Heartwood—Annual 
Rings—Spring and Summer Wood—Anatomical Structure of Broad-leaved 
Trees—Minute Structure—Grains of Wood—Color and Odor—Resonance— 
Weight a Function of Structure and Moisture—Variation of Weight in Single 
Trunk and in Species—Moisture Distribution—Drying Timber—Shrinkage 
explained—Effects of Shrinkage—Amount of Shrinkage—Mechanical Proper¬ 
ties—Stiffness—Strength as a Beam—In Tension and Compression—In 
Shearing—Influence of Weight and Moisture on Strength—Hardness— 
Cleavability — Flexibility — Toughness — Practical Conclusions — Chemical 
Properties and Technological Products—Wood as a Fuel—Charcoal Prod¬ 
ucts of Wood-distillation—Durability and Decay—All Decay produced by a 
Fungus-growth—Prevention of Decay—Structure as a Key to Identification 
of Species—A Structural Key to Species—Characteristic Structural Features 
i —Use of the Key—Descriptive List of the More Important Trees in the U. S., 
with Illustrations of Leaf and Fruit... 


i. ; __ 

1 . i: 

PART III. 

TESTING-MACHINES AND METHODS OF TESTING 
MATERIALS OF CONSTRUCTION. 

CHAPTER XIV. 

MECHANICAL TESTS IN GENERAL. 

General Observations—Tests Classified—Testing-machines—Effect of Rate of Load¬ 
ing—Significant Limits of Deformation—All Absolute Elastic Limits 
unsatisfactory—The “Apparent Elastic Limit”. 


CHAPTER XV. 

* 

TENSION TESTS. 

Significance of Tension Tests—Selection of Test Specimens—Preparation of Speci¬ 
mens—Standard Dimension of Tension-test Specimens—Tetmajer’s Analysis 
of the Elongation—Time Function of Tension Tests—Tension-test Machines 
—Gripping Devices—Special Machines—The Emery Testing-machine fully 
Described—Extensometers—Autographic Diagram Apparatus—Gauging Im- 
; i plements........ 






TABLE OF CONTENTS. 


xi 


CHAPTER XVI. 

COMPRESSION TESTS. 

PAG£ 

Objects of—Compression-test Specimens—Bedding the Specimen in the Machine— 
Compressometers—Column Tests—Strength of Column the same as its 
Apparent Elastic Limit—Considered Results—Tetmajer’s Results—Formulae 
for Strength of Columns—Spring Testing-machines. 353- 


CHAPTER XVII. 

CROSS BENDING TESTS. 

Object of—Essential Conditions of—Deflection measured in Testing Cast Iron— 

Modulus of Rupture—Modulus of Elasticity—Impact-testing Machines. 369 


CHAPTER XVIII. 

IMPACT AND HARDNESS TESTS. 

Object of Impact Tests—Essential Conditions of—Energy of the Blow—Hardness 
Defined—Test of Permanency of Form—The Rodman Punch Standardized— 

Test for Permanency of Substance—Turner’s Apparatus. 375 

CHAPTER XIX. 

SHEARING AND TORSION TESTS. 

Essential Conditions of Sheariug Tests—Occurrence of Shearing Stress in Practice 

—Shearing-test Appliances—Torsion Tests—Torsion-testing Machines. 385 


CHAPTER XX. 

COLD BENDING AND DRIFTING TESTS. 

Significance of Cold-bending Tests—Methods of making them—Results of Cold- 
bending and Tension Tests compared—Effects of Punching and Drilling 
developed by Cold-bending Tests—Combined Specified Requirements in 
Tension and Cold-bending—Results of Tensiou, Cold bending, and Impact 
Tests compared —Drifting Tests standardized.394 

CHAPTER XXI. 

THE TESTING OF CEMENT. 

Standard Scientific Tests of Cement—Test of Fineness—Significance of Fineness— 
Thoroughness of Burning tested by Specific gravity Test—Apparatus for— 
Rate of Setting Automatic Apparatus for Registering— Vicat’s Needle— 







Xll 


TABLE OF CONTENTS. 


PAGE 

Tests for Soundness—The Boiling Test—Tests of Strength—Fixed Relation 
between Tensile and Compressive Strength—Standard Consistency of Neat- 
cement Briquettes—Effects of Varying Percentages of Water—Normal or 
Standard Sand—Effect of using Different Sands—Consistency of Standard 
Mortar, 1 C : 3 S—Formation of the Briquettes—Form of the Briquette—A New 
Form proposed—Distribution of Stress over the Minimum Section—The 
Clips—Cement testing Machines—Eccentricity of Briquette in Clips—Cross- 
breaking Tests—Standard Tests of Adhesion—Normal Variations of Volume 
of Cement mortars in Air and in Water—Recommendations of the French 
Commission for testing Permanency of Volume—Test of Permeability of 
Cement-mortar—Test for Decomposing Action of Sea-water. 407 

CHAPTER XXII. 

TESTS OF THE STRENGTH OF STONE AND BRICK. 

Crushing Tests of Stone—Tests for Paving-brick—The Cross-breaking Test—The 
Crushing Test—The Rattler Test Standardized—Standard Tests of Com¬ 
mittee of the National Association of Brick Manufacturers. 456 

CHAPTER XXIII. 

TESTS OF THE STRENGTH OF TIMBER. 

Important Deductions from the U. S. Timber Tests—Description of the U. S. 
Timber Tests—Mechanical Tests—Cross-bending Test—Crushing-endwise 
Tests—Crushing across Grain—Shearing—Tension—Time Function.462 


PART IV. 

THE MECHANICAL PROPERTIES OF THE MATERIALS OF 
CONSTRUCTION AS REVEALED BY ACTUAL TESTS. 

CHAPTER XXIV. 

THE STRENGTH OF CAST IRON. 

Tensile Strength—Composition and Strength of High-grade Cast Iron—Compres¬ 
sive Strength—Cross-breaking Strength-Modulus of Elasticity—Kirkaldy’s 
Results—Shrinkage Stresses—Strength Increased by Impacts—Pipes and 
Columns. 469 


CHAPTER XXV. 

THE STRENGTH OF WROUGHT IRON. 

Strength with the Grain—Streugth across the Grain—Time Fuuction—Compressive 
Strength—Shearing Strength—Effect of Stressing beyond the Elastic Limit 
—Streugth of Chains. 482 








TABLE OF CONTENTS. 


xm 


CHAPTER XXVI. 

THE STRENGTH OF STEEL. 

PAGE 

Tensile and Compressive Strength—Effect of Varying Percentages of Carbon— 
Effect of Thickness—Effect of Finishing at a Low Red Heat—Effects of An¬ 
nealing on Low-carbon Steel—Tests of Steel by Punching—Quenching and 
Annealing—Billet Tests Characteristic of Final Rolled Forms—Elongation 
and Reduction—Compressive Strength same as the Elastic Limit—Elastic 
Limit in Compression for Various Kinds of Contact—Areas of Contact be¬ 
tween Wheels and Rails—Moduli of Elasticity in Tension and Compression 
—Annealing Effects after Overstressing—Effects of Varying Lengths of 
Reduced Section—Nickel Steel—Effects of Forging and Rolling—Steel- 
welded Tubes—I Beams and Plate Girders—Effects of Stressing beyond the 
Elastic Limit—Shearing Strength—Frictional Resistance of Riveted Joints— 
Friction per Square Inch of Rivet Section—Bearing Resistance of Plates— 
Tensile Strength of Grooved Plates—Injurious Effects of Punching and 
Shearing—Influence of Form of Thread on Strength of Screw-bolts—Steel 
Specifications. .490 


CHAPTER XXVII. 

THE FATIGUE OF METALS. 

Fatigue Defined—Micro-flaws in Steel—Wbhler’s Fatigue Tests—Limits of Stress 
for an Indefinite Number of Repetitions—A New Universal Formula for 
Dimensioning........ ..... 537 


CHAPTER XXVIII. 

STRENGTH OF THE COPPER-ZINC-TIN ALLOYS. 

Strength of Copper—Annealing Copper Wires and Plates—Strength of Brass- 

Strength of Bronze—Special Brouzes. 548 


CHAPTER XXIX. 

THE EFFECTS OF TEMPERATURE ON THE MECHANICAL 

PROPERTIES OF METALS. 

Effects on the Strength of Iron and Steel—The Change in the Elastic Limit- 
Change in the Modulus of Elasticity—Effect on Resistance to Impact- 
Effects on Copper and Bronze. . 


CHAPTER XXX. 

RESULTS OF TESTS ON CEMENTS, CEMENT-MORTARS, 

AND CONCRETES. 

Strength of Natural Cements—Strength of Portland Cements—Modulus of Elas¬ 
ticity of Cement-mortars—Strength of Sand cement Mortars—Variation of 






XIV 


TABLE OF CON TEATS. 


PAGE 

Strength with Increasing Proportions of Sand—Variation of Strength of 
Mortars with Varying Size of Sand-grains—Relative Economy of Coarse and 
Fine Sand-grains—Experiments with Sands of Artificial Granulometric Com¬ 
position-Porosity of Mortars as Affected by Size of Sand-grains—Effect of 
Long Storage on the Strength of Cement—Effect of Iiegaugiug after Set 
begins—Effect of Carbonic-acid Gas on the Hardening of Cement-mortars— 
Adhesive Strength of Cement-mortars—Compressive Strength and Elasticity 
of Cement and Concrete—Strength and Economy of Cement-mortars and 
Concretes—Filtration through Concrete—Effects of Freezing on Cement-mor¬ 
tars and Concretes—Anti-freezing Mixtures—Concrete Mixtures—Concrete 
Structures in Sea-water—Fire-resisting Qualities of Concretes—Properties of 
Cinder-concrete Mixtures—Cinder-concrete with Expanded Metal Base. 568 


CHAPTER XXXI. 

RESULTS OF TESTS ON STONE AND BRICK. 

The Building-stones—Weathering of Building-stones—Freezing Tests—The Sul- 
phate-of soda Test—Chemical Tests—Microscopic Tests—The Absorption 
Test—The Specific-gravity Test—Compressive Strength—Table of Physical 
Qualities of American Building-stones—Elastic Properties and Crushing 
Strength, with Stress-diagrams—Bauschinger’s Results—Resistance to Abra¬ 
sion—Bauschinger’s Abrasion Tests and Results—Strength and Elastic Prop¬ 
erties of Brick and Brick Piers, with Stress-diagrams—Results of Tests of 
Paving-brick—Results of Tests on Building-brick. 630 


CHAPTER XXXII. 

EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 

The Mechanical Tests of the U. S. Timber Investigations—List of Species Tested— 
Ultimate Ends of the Investigation—The Moisture Factor—Tables of Results 
on Thirty-two Species—Special Investigations—Relation between Strength 
and Weight—The Factor of Safety—Table of Safe Loads on Beams— 
Strength of Wooden Columns—How to distinguish between Short-leaf and 
Long-leaf Pine Lumber—Geographical Distribution of Southern Pines— 
Holding Force of Nails. 664 


CHAPTER XXXIII. 

STRENGTH OF IRON AND STEEL WIRE AND WIRE ROPE. 

The Strength of Wire—Strength of Steel-wire Rope—Methods of Testing the 

Strength of Wire Ropes—Shop Tests of Wire—The Albert-lay Rope. 691 






TABLE OF CONTENTS. 


xv 


CHAPTER XXXIV. 

THE MAGNETIC TESTING OF IRON AND STEEL. 

PAGE 

Magnetic Properties defined—Hysteresis—Measurement of Permeability—Induc¬ 
tive Methods—Traction Methods—Measurement of Hysteresis—Results of 
Tests—Development due to Testing—Conditions affecting Magnetic Quality 
—Importance of Magnetic Testing—Useful Data on Conductivity. 702 

APPENDICES. 

A. Biographical Sketch of Prof. Johann Bauschinger. 723 

B. Study of Iron and Steel by Micrographic Analysis. 725 

C. Comparative Analysis of the Resolutions of the Conventions, of 

the French Commission, and the American Society of Mechanical 
Engineers. 737 

D. Standard Specifications for Iron and Steel. 756 

E. The Commercial Analysis of Portland Cement. 772 

F. The Preservation of Timber. 775 


















.. . 


- 

. ...... 
















THE 


MATERIALS OF CONSTRUCTION. 


PART I. 

SYNOPSIS OP THE PRINCIPLES OF MECHANICS 
UNDERLYING THE LAWS OF THE 
STRENGTH OF MATERIALS* 


CHAPTER I. 

GENERAL NATURE OF DEFORMATION AND STRESS. 

1. Elastic and Plastic Bodies. —An elastic body is one which, when 
deformed under the application of an external force, will recover its origi¬ 
nal dimensions when the deforming force has been removed. A plastic 
body is one which will not recover its original dimensions after deforma¬ 
tion. A body which will fully recover its original dimensions after defor¬ 
mation is said to be perfectly elastic. When it will only partially recover 
its original dimensions after deformation it is said to be partially elastic, 
and to the extent of its failure to recover its original form it may be said 
to be plastic. 

All solid bodies are nearly or quite perfectly elastic up to a certain limit 
of deformation, beyond which they become partly elastic and partly plastic. 
This limit within which the body is nearly or quite perfectly elastic is 
called the elastic limit. When deformed beyond this limit the body will 
recover a portion of such deformation, the rest remaining as a permanent 
change or set. Beyond the elastic limit, therefore, a body may be said to 
be partly elastic and partly plastic. Practically all the materials used in 
engineering design may be said to be perfectly elastic within certain limits; 
and as these elastic limits are well beyond the limit of maximum loading in 


* This Part is intended to be supplementary to the matter contained in text-books on 
applied mechanics, rather than to replace such courses. 






2 


THE MATERIALS OF CONSTRUCTION. 

practice, it is customary to regard all engineering materials as perfectly 
elastic for all practical purposes. 

2. Stress and Deformation. —The deformation which a solid bod}^ suffers 
on the application of an external force has commonly been called strain, 
but in this work it will be designated deformation simply.* The deforma¬ 
tion which is fully recoverable on the removal of the external force may be 
-called the elastic deformation. That which remains as a permanent set 
after the external force has been removed may be called the plastic defor¬ 
mation. Within the elastic limit the deformation is wholly elastic. 

The relative deformation is the proportionate distortion, or the linear 
change divided by the original length of dimension in the direction of the 
deforming force. Thus if a bar 10 inches long be stretched 0.01 inch, 
then this 0.01 inch is the deformation, and the relative deformation is 0.01 
divided by 10, or 0.001 inch. Thus the actual deformation is a concrete 
quantity, and is measured in units of length, while the relative deformation 
is an abstract number, and may be defined as the ratio of the distortion to 
the original length. This relative or proportionate deformation may also 
be defined as the deformation per unit of length. 

Stress may be defined as the resistance a solid body offers to the defor¬ 
mation produced in it by the action of an external force, and it may also be 
defined as the resistance to this external force directly. Under the law 
that action and reaction are equal, the stress must be quantitatively equal 
to the external force, and it may be regarded as resisting this external 
force, or these two may be regarded as being in equilibrium. Since the 
application of an external force to a solid body, however, is always accom¬ 
panied by a deformation of that body, and since this deformation disap¬ 
pears on the removal of the external force, the internal stress in tiie body 
may be said to be developed as a resistance to this deformation, and in this 
sense the deformation may be regarded as the immediate cause of the stress, 
the ultimate cause being the external force. 

3. Proportionality of Stress and Deformation Inside the Elastic Limit.— 
Within the limits of perfect elasticity of solid bodies the deformation is 
directly proportional to the external force producing that change of form; 
and since the internal stress is of necessity equal to the external force, we 
arrive at this important proposition: Inside the elastic limit the stress is 
directly proportional to the deformation ivhicli accompanies it .f This 

* The word strain is used in common language in several other senses, so that its use 
in this specific scientific sense, though warranted, is of doubtful propriety. The author 
has so used it, however, in his previous works. 

t This law was first announced by Robert Hooke in 1676, in the form of an anagram, 
as “The true theory of elasticity or springiness ceiiinosssttuv.” Two years later the 
key to this anagram was given in the Latin phrase “ Ut tensio sic vis," a free rendering 
of which would be, “As the extension so is the strength.” This law of proportion¬ 
ality, therefore, between the stress and the deformation within the elastic limit is fre¬ 
quently referred to as Hooke’s Law. 






GENERAL NATURE OF DEFORMATION AND STRESS. 


3 


proposition may be stated in another way by saying that inside the elastic 
limit the stress per unit area divided by the proportional deformation is a 
constant for any particular solid body. Since this constant is the ratio of 
the deforming force to the accompanying deformation of any particular 
solid body, it is evidently an important function, and it has therefore been 
given a name. The name of this ratio is the modulus of elasticity. We 
have, therefore, 


Modulus of elasticity — E = 


stress 

deformation 9 



wherein by stress is meant stress in pounds per square inch, and by defor¬ 
mation is meant a proportionate change, or the deformation per unit of 
length. Thus if an external pull, P, be applied to a bar whose cross-section 

P 

is A, then the unit stress is —; and if the length of the bar be l, and its 
actual extension under the application of this external force be a, then the 

(X 

deformation, or proportionate distortion, wtfuld be y, whence we should have 


P 

j, A _ PI _pl 

a Aa a 

i 



wherein p is the stress in pounds per square inch. Thus if the external 
force of 60,000 pounds be applied to a bar whose length is 10 inches and 
whose cross-section is 2 square inches, and if the extension under this load 
be 0.01 inch, we should have 


PI _ 60,000 X 10 
Aa~ 2 X 0.001 


30,000,000. 


That is to say, such a material would have a modulus of elasticity of 
30,000,000; and this is about the average value of the modulus of elasticity 
of steel. 


Example .—If steel rails be welded together at a temperature of 80 F., what 
will be the total tensile stress in an 80-pound rail at a temperature of 20° below 
zero, and what will be the compressive stress in this rail at a tempeiatuie of 140 F., 
the coefficient of expansion being assumed as 0.0000065 per degree F.? 


In solving such a problem as this, since the length of the rail cannot 
change for a change of temperature, the contraction which would occur if free 
to move is overcome by the application of a sufficient external force coming 
from the surrounding bodies to prevent this contraction. In othei words, 
an external force is developed just sufficient to stretch the body as much as 
it would contract under a fall of temperature, and similarly an external 
force is exerted to compress the body as much as it would expand under a 








4 


THE MATERIALS OF CONSTRUCTION. 


rise of temperature. We have then only to determine the amount of the 
contraction or expansion from temperature and call this the deformation 
produced by the application of an external force, and then by the aid of the 
modulus of elasticity find the amount of this external force, and divide it by 
the area of the cross-section of the rail, thus obtaining the internal stress in 
pounds per square inch. The cross-section of the rail is indicated by its 
weight. The weight of rails is always given in pounds per yard, and it so 
happens that a bar of iron or steel one inch square and 36 inches long 
weighs just ten pounds. This unit is called an inch-yard. Therefore an 
80-pound rail has just eight inches of cross-section. With the above 
information the student is prepared to solve the problem. It is evident that 
the length need not be considered; or any length may be chosen, as, for 
instance, one inch, since only the proportionate change of length need be 
considered in either case. The answers to the problem are 156,000 pounds 
total stress in tension at the lower temperature and 93,600 pounds total stress 
in compression at the upper temperature, the stress per square inch being 
19,500 pounds in tension and 11,700 pounds in compression, respectively. 
Since the elastic limit in both tension and compression of this grade of steel 
is about 45,000 pounds per square inch, it is evident that these stresses are 
well within these elastic limits, and hence no injury to the rail would ensue 
from the prevention of expansion and contraction in this manner. 

" 4. Different Kinds of Deformation and Stress. —Under the application of 
suitable external forces there are commonly recognized five kinds of defor¬ 
mation, namely: Extension, Compression, Angular, Bending, and Twisting; 
and corresponding with these are five kinds of stress, namely: Tensile, 
Compressive, Shearing, Bending, and Tortional. The last two kinds of 
stress are really combinations of the other three. Thus, bending stress may 
be resolved into tension and compression, with or without shearing, and a 
tortional stress is a particular kind of shearing stress. For any particular 
kind of material there is a definite relation between these several deforma¬ 
tions and their corresponding stresses. The numerical values of the ratios 
of these corresponding deformations and stresses are the moduli of elasticity 
in the several cases. It so happens, however, that the modulus of elasticity, 
or the ratio between the stress and the deformation in tension, is usually the 
same as it is in compression. Both tension and compression are called direct 
stresses, and hence we may in general speak of the modulus of elasticity in 
direct stress, and the modulus of elasticity in shearing, in cross-bending, and 
in torsion. Since cross-bending distortion gives rise mostly to distortion 
in extension and compression, and their corresponding stresses, the modulus 
of elasticity in cross-bending may also be said to be the same as that in 
direct stress. 

The modulus of elasticity, therefore, which is used in tension, compres¬ 
sion, and cross-bending, is one and the same, and is sometimes spoken of as 
Young’s modulus. That is to say, it is the ratio between direct stress in 


GENERAL NATURE OF DEFORMATION AND STRESS. 5 


pounds per square inch and the corresponding proportionate linear defer - 
mation. 

5. Longitudinal and Lateral Deformation under Direct Stress. —The lon¬ 
gitudinal deformation of a solid body in the direction of the deforming force 
is A l, where l is the original length in this direction and A is the proportion¬ 
ate deformation. Hence we may write, for Young’s modulus, 

E __ stress per unit area p 

deformation per unit length ~ A. 


It is a fact of observation that when a metal body is elongated by an exter¬ 
nal force from l to l + XI (inside the elastic limit), it contracts laterally about 
one fourth of its proportionate elongation. Hence if the original diameter 

A 

were d, its diameter after stretching would be d — -d. This ratio of lateral 

to longitudinal deformation, under longitudinal external forces, is called 
Poisson’s ratio. It is usually taken as £ for all metals, but for india-rubber 
it is J. The true values of this ratio, for some of the more common mate¬ 
rials, are: * 


Glass . 
Steel . 
Copper 


0.2451 

0.268G 

0.3270 


Brass . . 
Delta-metal 
Lead . . 


0.3275 

0.3399 

0.4282 


6. Change of Volume under Direct Stress. —If the length of the body is 
increased by XI, and its lateral dimensions are decreased by \Xd, the new 
volume for a rectangular bar having lateral dimensions of b and d would be 


10 + *) • *(i - J) • d[i - J) = m{ i + |). f 

But the original volume was Ibd, hence the change of volume is Ibd^ 

/v 

A A 

and the relative change is Ibd— divided by the original volume = 7 , or the 

2 2 

volume has been increased by one half as great a percentage as the length 

was increased. 

If we should now apply an equal direct tension in the direction of b, we 

A 

would increase this dimension by A b, and the volume by -Ibd, and similarly 
for a tensile force in the direction of d. Hence for a direct tensile force in 


* Taken from Wertlieim and given in the Report of the French Commission cles 
Meihodes d’Essai des Materiaux de Construction , 1895, vol. in. p. 6. 

f Since A is very small as compared to unity. The product of ( l + m)(l -f n){l p), 
etc., where m, n, and p are very small fractions, is l + (m -f- n-\-p), since the products 
of the auxiliary terms can he neglected. 






6 


THE MATERIALS OF CONSTRUCTION. 


all three planes the volume would be increased by fA times its original vol¬ 
ume, and each dimension by |-A times its original measure. 

For a compressive force in all directions the volume would be diminished 
to (1 — f A) times its original volume, and each lineal dimension to (1 — JA) 
times its original measure. 

The volumetric change of a solid body for an equal stress applied in all 
directions is therefore f of the change of the dimension in the direction of 
an equal simple longitudinal stress. Thus the longitudinal proportionate 
deformation for a direct stress of p pounds per square inch is A, or 



But since the relative volumetric change for stress in all directions is 
|A, we have as the ratio between volumetric stress and deformation under 
an equal stress in all directions, as a fluid pressure for instance, 




whence 

Ev = \E. .(4) 

That is to say, the volumetric modulus of elasticity of a solid body for an 
equal stress in all directions is § of Young’s modulus, which applies only to 
direct stress in one plane and its accompanying deformation.* 

7. Angular Deformation under Direct Stress. —We will here consider one 

case only of angular deformation under 
direct stress, and that is for equal di¬ 
rect stresses of opposite signs on planes 
at right angles to each other, as shown 
in Fig. 1. If the original length of 
each side of this cube be l, then the 
dimension in the direction of f will be 
increased as much by the action of the 
vertical compression V as it will be 
diminished by the action of the hori¬ 
zontal tension H, since V — H in 
pounds per square inch. Also the 
cube will be shortened in the direction l 3 by an amount A l due to the force 



* This statement applies only to bodies in which Poisson’s ratio is v. Since this 
ratio is very nearly ^ for india-rubber, it follows that the cross-section is reduced as 
much as the length is increased, under a tensile stress in one plane, and hence the 
volume remains unchanged. Similarly, for a compressive stress in all directions the 
volume is unchanged (almost); so that while Young’s modulus of elasticity for this 
material is very small, the volumetric modulus is very great; and if Poisson’s ratio were 
quite F the volumetric modulus would be infinite, or it would t»e quite incompressible. 
It is probably the most incompressible of any known substance. 

















GENERAL NATURE OF DEFORMATION AND STRESS. 


7 


I, and by 4 this amount due to the lateral force II. Also the dimension in 
the direction f will be elongated by A l from the action of the horizontal 
foice H, and by 3 - this amount from the force V. Hence the final dimen¬ 
sions in these directions will be /(I — f A) and /(I -f- |A) respectively. 

If in the front face of this cube the lines ABCD be drawn, joining the 
middle points of the edges before deformation, this figure is a square. After 
deformation, if we make the point at A common to the two figures, we 
have the points B, C, and D moved to B', O', and D' respectively. This 
produces an angular movement of one of these lines equal to the angle 
BAB', which we will call 6. This is now one half the deviation of the 
angles B'AD', B'C'D', AB'O ', and AD'O' from right angles. 

But since BG — GB' — £(f-A l), B' falls on BO. 

Also, 


tan 6 = 


BB' 

AB 


(from similar triangles) 


BG_um 

AF \l 



Or, since 6 is small, we may say, 

6 = f A, where 6 is given as arc in terms of the radius as unity. 

But 6 = \ the deviation of the angles AB'O', B'O'D', etc., from right 
angles. Hence we have 


2 6 — angular change = 2(fA).(5) 

equals twice the linear deformation. 

That is to say, two direct stresses at right angles to each other and of 
opposite signs produce in the plane of the stresses an angular deformation 
equal to ticice the proportionate linear deformation. This result will be 
used in Art. 9 in obtaining the ratio of the modulus of elasticity in shearing 
to that in direct stress. 

8. Relation between Shearing and Direct Stresses.—In Fig. 2 let the 

square ABCD represent a very small portion 
of a longitudinal section of a body, taken in 
the plane of the forces. Assume also that 
there are shearing forces acting on the body, 
which have developed at this point in this 
plane a shearing stress on the vertical sides 
equal to s 1 pounds per square inch, these 
forming a couple and producing a turning 
moment. Evidently this particle can only 
be held from turning in this plane by the 
development of an exactly equal shearing 
stress (or resistance) on the horizontal faces, 
which will give an opposing couple and 
moment of resistance equal to the turning moment of the origina. shearing 



Fig. 2. 










8 


THE MATERIALS OF CONSTRUCTION. 


forces. If the lengths of these sides be equal, we shall then have s 2 = s x ir 
pounds per square inch. Hence we may say: 

A shearing stress in one direction at any point in a body develops an 
equal opposing shearing stress at right angles to it in the plane of the 
resultant external forces. 

But the two sets of shearing forces indicated in the figure will tend to 
deform the body by elongating it in the direction ED , and shortening it in 
the direction AC. The internal resistance to such a deformation develops 
in the body a direct tensile stress or resistance along the line A C and a 
compressive stress along the line ED. 

If S J — S 2 represent the total shearing stresses on the vertical and hori¬ 
zontal sides of this particle, respectively (s, and s , being equal intensities of 
stress, or stress in pounds per square inch), then we may resolve these along 
the diagonals and. obtain 

total tensile stress on AC = V Sf -f- Sf = V sfAE 2 -j- sfBCt 

= sVaB* + 1BC* = sAC= T 
= total compressive stress on BD = v S' + = C, 


or these two direct stresses also are equal. 

But the stress per square inch is the total stress divided by the area 
over which it acts; hence we have for the intensities of the tensile and 
compressive stresses 


T _ C 
AC~ ED 





Hence we have the larger conclusion that 

A shearing stress in one direction at any point in a body develops an 
equal opposing shearing stress at right angles to it in the plane of the exter¬ 
nal forces , and these opposing shearing stresses produce tico opposing direct 
stresses acting at 45° with the shearing stresses and at right angles to each 
other , these tensile and compressive stresses having the same intensities , in 
pounds per square inch , as the original shearing stress. 

9. The Shearing Modulus of Elasticity.—The modulus of elasticity in 
shearing may be defined as the ratio of the shearing stress in pounds per 
square inch to the accompanying angular deformation. By angular 
deformation is here meant the angular change, as derived in Art. 7, where 
2 6 is a pure ratio, being the ratio of arc to radius. From the last article 
we know that a shearing stress gives rise to direct stresses at right angles to 
each other, of opposite signs, but of equal intensities; and when such stresses 
act, we learned in Art. 8 that the proportionate angular change was twice 
the proportionate linear change when equal direct stresses were acting at 
right angles to each other. But when both of these stresses were acting 
we found the linear change to be JA, or f that due onlv to the deformiim 

* b 












GENERAL NATURE OF DEFORMATION AND STRESS. 


9 


force iu that direction; and, as found in equation (5), 20 = 2(fA), we have 
20 = |A. 

7 ) 

But E = Young’s modulus of elasticity = ^ 


and 


E s = shearing modulus of elasticity — ^ 

shearing stress per square inch 
angular deformation 

But we have shown, when s = p, 20 = hence we have 


f - — = JL = - E - 

s 2d |A 51" 

That is to say, E s = f E, or the shearing modulus of elasticity = | of the 
linear or Young’s modulus* 



* This conclusion is based on a value of Poisson’s ratio of i. The general relation 

E, where m is the reciprocal of Poisson’s ratio. 


, 3 1 m 

between E s and E is E s — = - — t—z 

20 2m+l 


Thus if this ratio be i, which it is approximately for brass and copper, then m = 3 and 
E s = | E, while for india-rubber, where m = 2, we have E s — \E. Prof. Bauscliiuger’s 
tests on round bars of steel give E» = 13,600,000, while for square bars of the same 
material he found E s = 11,500,000, thus showing a failure of the theory to harmonize 
results on these two forms of cross-section even inside the elastic limit. See Rep. 
French Commission, vol. hi. p. 208, for Bauschinger’s results. 




CHAPTER II. 


MATERIALS UNDER TENSILE STRESS. 

% 

10. General Phenomena accompanying Tensile Tests.—When a body of 
uniform cross-section is subjected to the action of an external force which 
tends to pull it asunder, it is elongated in the direction of this force by a 
proportionate amount equal to the average force per square inch divided 
by its modulus of elasticity; thus 

A = the proportionate elongation = 

where p is the external force, or internal stress, in pounds per square inch, 
and E is the modulus of elasticity (Young’s modulus). 

At the same time its lateral dimensions are reduced by one fourth as 
great a percentage as that which represents the proportionate elongation, as 
described in Art. 5. This rate of elongation in the direction of the force, 
and contraction in its transverse dimensions, continues in strict proportion 
to the amount of the external force, until the elastic limit is reached, when 
both the longitudinal elongation and the transverse contraction begin to 
increase at a more rapid rate, until finally, with the more ductile metals, 
the condition of perfect plasticity or viscosity is reached, and the body 
elongates under a constant force, while the lateral dimensions reduce more 
and more, until rupture finally occurs. 

If the external force or load, in pounds per square inch, be represented 
by vertical ordinates, and the corresponding elongations be represented by 
horizontal abscissa?, then the action of the specimen under test may be 
indicated by what is known as a stress-diagram, the vertical coordinates 
representing stress, and the horizontal coordinates the corresponding defor¬ 
mations. In Fig. 3 such stress-diagrams are shown for timber, cast iron, 
wrought iron, and steel. These lie on the upper side of the horizontal 
axis. If the same materials were to be subjected to compressive external 
forces, corresponding stress-diagrams might be drawn in opposite direc¬ 
tions, that is to say, downward and to the left, as indicated in Fig. 3, below 
the horizontal axis. 

In a complete stress-diagram of a ductile metal there are four signifi¬ 
cant points which need to be noted. These are: the true elastic limit , 
the apparent elastic limit , the ultimate strength } and the breaking -point, 

10 


MATERIALS UNDER TENSILE STRESS. 


11 


These four significant points in a tension stress-diagram are indicated by 
the letters A, B, C, and D in Fig. 4, where the same diagram is drawn to 
widely different horizontal scales. 

Thus the point A is the true elastic limit, or the ratio of the stress to 
the deformation is a constant from the origin to this point. This requires 
that the stress-diagram should be a perfectly straight line from 0 to A, 
Beyond the elastic limit, or above A, the deformation sometimes increases 
somewhat more rapidly than it did below A, and the locus then becomes 
somewhat curved from A to B. At B a very marked change occurs in the 



Fig. 3. —Typical Stress-diagrams of Timber. Cast Iron, Wrought Iron, and Steel in 
Tension and Compression, drawn to the same scales. 

specimen in the case of wrought iron and structural steel. If the test be 
continued slowly at this point, it will be found with the more ductile 
metals that the specimen elongates a considerable amount under a nearly 
constant load, as shown in the diagram, from B to B '. This point is 
called the “ apparent elastic limit,” or the “ yield-point” or the “ breaking- 
down point.” In ordinary commercial testing of iron and steel this point 
is always called the “elastic limit,” and the true elastic limit, or the point 
A , is not found. This results from the rapid and somewhat crude methods 




















































































12 


THE MATERIALS OF CONSTRUCTION. 


used in making commercial tests, and the author of this work has some¬ 
times called this “ apparent elastic limit ” the “ commercial elastic limit,” 
since it is the so-called “ elastic limit” found in practically, all the tests 
made by American inspection bureaus and rolling-mills. Since this yield- 
point has been so long regarded as the “elastic limit,” whereas the point 
A is the true elastic limit, persons who wish to be accurate and at the same 



Fig. 4. 

time to be understood find difficulty in conveying their meaning.* The 
terms “yield-point” and “breaking-down point” are not in common use, 
while the term “elastic limit” is commonly misused. In the present state 
of knowledge on the subject, therefore, the terms “ true elastic limit” and 
“ apparent elastic limit” probably would best describe the points A and B 
respectively.! It has been the practice of the author, in making tests to 
be used commercially, to call the point B the “ elastic limit,” without any 
explanation or exception, when he desired his results to be comparable 
with those made elsewhere for commercial purposes. 

Just what happens to the specimen at the point B is well shown on 
Plate I, l which is a reproduction of a photograph of specimens of polished 

* Fortunately, in the ease of soft, or structural, steel these true points are practically 
identical, so that in this material no such distinction of terms as is here proposed are 
necessary. See Figs. 5, 6, 7, and 8. 

f The French Commission use this term “ apparent elastic limit ” for the point B. 

X The author has not seen elsewhere as clear indications of the action of such ma¬ 
terials at the “yield-point.” The tests shown on Plate I were made by him and photo¬ 
graphed in March, 1892. The bars were polished to a mirror surface before testing. 
These photographs were exhibited at the Engineering headquarters at the World’s Fair 
Chicago, 1893, and while they were much observed and studied, it did not appear that 
any one had ever seen such clear “ breaking-down ” indications before. The significant 
fact is that these effects come instantly, as to any particular marking, and that they sue- 











PLATE I. 



Photographs of a Polished Steel Bar, 1 in. x 2 in,, after Bending and after 
Pulling, showing the “ Biieaking-down ” of the Metal. 

The tensile test was interrupted before the breaking-down action had extended 
entirely throughout the length of the bar. (Tested and photographed by the author, 
1892.) 










MATERIALS UNDER TENSILE STRESS. 


13 


steel subjected respectively to a uniform bending moment and to a tensile 
stress. This photographic reproduction shows how the tension specimen 
fails or “ breaks down” its molecular arrangement in detail by shearing on 
inclined sections, beginning at the end of the specimen where it was held 


-00000 

SS00U 

S0000 

SSM? 

20000 

04000 

44000 

24000 

20000 

Z0000 

/07M 

.... 







/ 









/ 

































£ 







\i 















2 0T/0\0 

' //V | 

00V- 

/22\? 

0 c 3)0, 

4i£ 

0 

0000 

0 

. 0.02A 
_ 

IN- 0.00L 

? 0.07, 

r 0/00 

0/2/ 

0./S6 

’ a/m 

£10N. 

22 T/0 

V /A/ 

8/JV- 


'. SC A 

LE 


0 0.S0&- /-0O AS0 2.00/0- 

p IG> 5 .—Autographic Stress-diagrams of Mild Steel, taken simultaneously with the 
Gray Extensometer Apparatus. Time, 2£ minutes. 

by the grips. The breaking down proceeded from the ends towards the 
centre. In this case the test was stopped before it had reached the middle 
portion. This central portion, therefore, is in its original or normal con¬ 
dition, while the remaining portions have been broken down in an irregular 

ceed each other regularly along the bar, like the formation of ice-crystals on freezing 
water. The markings on the tension bar, or on the tension side of a beam, are depres¬ 
sions, while on a compression bar, or on the compression side of a beam, they are 

swellings. 



































14 


THE MATERIALS OF CONSTRUCTION'. 


weblike pattern. If the test had been continued, this action would have 
gone on from the ends towards the centre, until the entire specimen had 
yielded in this manner; and when this breaking-down action had developed 
over the entire length o{ the specimen, the point B r in the diagram would 
have been reached. This breaking-down action, therefore, all occurs over 



Fig. 6. —Typical Stress-diagram of Mild Steel, plotted to two scales. (From 

records of Tests of Metals, Wat. Ars., 1886.) 

the entire length of the specimen between the points B and B\ and the 
reason why B stands above B' seems to be that it requires a greater force to 
start this breaking-down action than is necessary to continue it and extend 
it throughout the length of the specimen after it has once been started. 
See Figs. 5, 6, 7, and 8. In Figs. 7 and 8 the true elastic limit is well 
above the yielding resistance of the metal, or the point A is above B. 





























MATERIALS UNDER TENSILE STRESS. 


15 



&G. 7.— Tension Tests of Wrougbt-iron Shafts 1 in. in diam., used for endurance tests. 
Average ultimate strength = 50,400 lbs, per sq. in.; average elongation = 27# on a 
length of 11 diameters. (Wat, Ars. Rep., 1890.) 














































































































16 


THE MATERIALS OF CONSTRUCTION. 


After tins breaking-down action has extended over the entire length of 
the specimen, a further increase in the load will continue to stretch the 
specimen nearly uniformly throughout its length, with a uniform reduction 



in cross-section, until at last the elongation and reduction continue under a 
constant load. That is to say, the stress-diagram becomes horizontal at the 
point C, Fig. 4. This marks the load under which the material is perfectly 
plastic or viscous, or for which the distortion continues with no increase of 
load. 

























































































MATERIALS UNDER TENSILE STRESS. 


17 


After passing the point C the specimen begins to show the marked 
reduction of cross-section at a particular point, which will ultimately be 
the plane of rupture. This action is indicated in Fig. 10. As soon as this 
‘ necking-down ” begins, the elongation continues under a diminishing 
load, as shown by the dropping of the locus in the stress-diagram, and the 
remaining portion of the elongation of the specimen nearly all occurs in 
this immediate vicinity. The area of cross-section becomes less and less, 
until at rupture it is perhaps less than half the original area, as shown 
in Fig. 10. 

„ 11. The Significant Results of a Tensile Test.—There are five signifi¬ 
cant results of a tensile test, namely: 

The Modulus of Elasticity; 

The Elastic Limit; 

The Ultimate Strength; 

The Percentage of Elongation; 

The Reduction of Area of Cross-section. 

The Modulus of Elasticity is found by dividing any stress per square 
inch below the elastic limit by the corresponding proportionate deforma¬ 
tion. Since the stress-diagram is a straight line from the origin to the 
elastic-limit point, any point on this portion of the locus may be selected 
for the determination of the modulus of elasticity. For instance, if the 
point which represents an elongation of 0.1 of one per cent be chosen, the 
deformation being 0.001 (see Fig. 6), the modulus of elasticity is found 
at once by multiplying the corresponding stress in pounds per square inch 
by 1000.* In other words, the modulus of elasticity is the tangent of the 
angle which that portion of the stress-diagram below the elastic limit forms 
with the horizontal axis when the two coordinates are properly evaluated 
by the vertical and horizontal scales respectively. 

It is a very remarkable fact that the modulus of elasticity of all grades 
of wrought iron and rolled steel, from the softest up to the highest grade of 
spring steel, is nearly constant, and has a value from 29,000,000 to 
30,000,000, being perhaps always within the limits of 27,000,000 and 
31,000,000 pounds per square inch. The ultimate strength of these metals; 
varies from about 45,000 to several hundred thousand pounds per square 
inch for the strongest steel wire; but through this range of variation of 
strength the ratio of the stress to the corresponding deformation re¬ 
mains nearly constant. The modulus of elasticity is, therefore, a very 
valuable quality of such materials and one which is made great use of in 

* If the diagram is not straight to Ibis point (lias its elastic limit below this point), 
then draw a tangent to the diagram at the origin, and note where it cuts the ordinate' 
marking a. deformation of 0.001, and this stress multiplied by 1000 is the modulus of 
elasticity. This modulus can be read off in this manner from any of the stress dia¬ 
grams for tension and compression found in this work. 





18 


THE MATERIALS OF CONSTRUCTION. 


engineering design. It may be called the modulus of stiffness, since it is a 
direct measure of the rigidity of a body, or an inverse measure of its flexi¬ 
bility.* 

«- 12. The True Elastic Limit is, in general, from 50 to 70 per cent of the ulti¬ 
mate strength of the material, while the apparent elastic limit is from GO to 
70 per cent of the ultimate strength of the material. The apparent elastic 
limit, or the breaking-down point, is also the ultimate strength for practical 
purposes, since almost all materials lose their value in structural designs 
after they have been deformed beyond this limit. 

The true elastic limit may be defined either as the deformation where 
permanent set begins, or as a point beyond which a given increment of load 
|iroduces a greater increment of deformation, which is the point where the 
ratio of the stress to the deformation ceases to be a constant and begins to 
diminish. This is also the upper extremity of the straight portion of the 
stress-diagram. If a material like wrought iron or structural steel be loaded 
beyond its true elastic limit, and even beyond its yield-point, and the load 
removed, the material has been permanently elongated; but if it again 
be subjected to a load, it will be found to be perfectly elastic up to the limit 
of its previous loading. In other words, its elastic limit has been raised to 
the value of its previous loading. In this way the elastic limit can be raised 
practically up to the ultimate strength. When the term “ elastic limit ” is 
used in a scientific sense without modification, the true or primitive elastic 
limit (point A, Fig. 4) is always to be understood; but when used in a com¬ 
mercial sense, the apparent elastic limit or yield-point (point B) is to be 
taken. 

As stated previously, the elastic limit is usually found in commercial 
testing by noting the action of the weighing-beam in dropping under an 
increasing stretch, this being in fact the breaking-down point. To determine 
the true elastic limit it is necessary to use very delicate measuring appli¬ 
ances, which will enable the observer to discover when the ratio of stress 
to deformation has begun to change. Even when using such devices the 
readings must be plotted to a large scale to detect the deviation from a 
.straight line. 

13. “ The Apparent Elastic Limit” is defined by the French Commission 
as “the load per square millimeter of the original section, where the defor¬ 
mation begins to increase sensibly with no increase in the external force 
applied (corresponding to the dropping of the beam in testing-maehines).”f 
Since in most kinds of materials there is no such point other than the ulti- 

* A modulus of flexibility would be the reciprocal of the modulus of elasticity, or —. 

E 

but Prof. A. B. W. Kennedy has taken for such a modulus of “ specific extension” the 
stretch in thousandths of an inch on a length of 10 inches under a stress of 1000 lbs. per 
sq. in. Its reciprocal multiplied by 10,000,000 is the modulus of elasticity. 

f Report of the French Commission, vol. i. p. 207. 



MATERIALS UNDER TENSILE STRESS. 


ID 


mate strength, and since in these materials an elastic limit corresponding to 
sensible deformations is required for practical purposes, the author proposes 
to extend the meaning of this term so as to make it applicable to all elastic 
materials, and at the same time to make it serve as the “elastic limit” to 
be universally used in all kinds of practiced tests. For this purpose he 
employs the following definition: 

The apparent elastic limit is the point on the stress-diagram of any 
material, in any kind of test, at which the rate of deformation is fifty per 
cent greater than it is at the origin* 

This point is found either by comparing increments of deformation with 
given increments of load, or better by plotting the stress-diagram and draw¬ 
ing a tangent to it which has an inclination to the vertical 50 per cent greater 
than has the tangent to the diagram at the origin, as shown in Fig. 9. To 



tlo this lay off the tangent to the curve at the origin (or inside the true 
elastic limit, where it is a straight line), and then fix a point on any hori¬ 
zontal line of the paper, 50 per cent farther from the vertical axis than the 
point where this tangent cuts it. Lay a parallel ruler on this point and the 
■origin, and move it till it becomes tangent to the curve and draw the tan- 


* This definition should not be made to apply, however, to materials not perfectly 
•elastic within any limits Thus certain stones and concretes have stress-diagrams which 
are reversed curves, their rates of deformation being greater at first than after they are 
heavily loaded, and any load produces a permanent set, as shown in Chapter XXXI. 
Here the modulus of elasticity is different for every increment of load, and no kind of 
“elastic limit” can be attributed to them. That is to say, they are not perfectly 
•elastic for any load however small. 





























20 


THE MATERIALS OF CONSTRUCTION. 


gent line. Then fix the point of tangency by the eye, and call this the 
apparent elastic limit.* 

This fixes a point which in all cases corresponds to an extremely small 
permanent deformation. In Fig. 9 the permanent deformation at this 
limit, for hard-drawn steel wire, is abont 0.0003 of the length, or T |~ (T of one 
per cent, while the limit so fixed is some 22,000 lbs. per sq. in. above the 
true elastic limit. Although this test was made at the U. S. Arsenal at 
Watertown, Mass., and on the Emery testing-machine, with extreme accu¬ 
racy, as shown by the accordance of the results when plotted to the large 
scale in Fig. 9, yet the “ elastic limit ” as set down in the published record 
(which “elastic limit” is supposed to be the “ true elastic limit”) lies some 
S000 lbs. per sq. in. higher than the “ apparent elastic limit ” fixed by the rule 
here laid down! This same state of affairs is shown in numberless cases in 
the recorded results of tests made at this the most fruitful and accurate labo¬ 
ratory in the world.f While, therefore, objection would be quickly raised 
to the criterion herein proposed for fixing an “apparent elastic limit” in so 
arbitrary a manner, and apparently so far beyond the “ true elastic limit,” yet 
no one would be inclined to question the records of the IT. S. Watertown 
Arsenal tests, in the fixing of a “true elastic limit,” even though this should 
in nearly all cases lie beyond this conventional “apparent limit ”! After a 
great deal of thought and research given to this subject, the author believes 
no better criterion can be found for fixing a practical “ elastic limit” which 
will be one and the same limit for a given material in the hands of all ex¬ 
perimenters, and on all machines. For all materials which have a definite 
“yield-point” this “apparent elastic limit,” determined as here described, 
will agree with it exactly; but for such materials it would never be deter¬ 
mined in this manner, since it is then so much more readily found bv the 
“ drop of the beam,” or even by a pair of dividers set to given marks on the 
specimen. For all materials which have no point of “ yielding under a 
fixed load” at this stage of the test, this criterion would always accomplish 
the following results: 

1. It would always fix one and the same well-defined point. 

2 . This point would always correspond to so small a permanent defor¬ 
mation as to be, for all practical purposes, the true elastic limit. 

3. It is equally applicable to all materials which, have an elastic field. 

4. It is equally applicable to all kinds of tests, whether on specimens or 
on finished members or structures, where deformations of any kind can be 
correctly measured. 

While the 50 per cent increase in the rate of deformation is purely arbi- 

* The author has done this in his U. S. timber tests since 1891, calling this point in 
his cross-bending stress,-diagrams “the relative elastic limit.” 

+ See other instances in records selected therefrom for this work in Chapters XXV 
and XXVI. 








MATERIALS UNDER TENSILE STRESS. 


21 


trary, it is not large enough to fix a point having an appreciable permanent 
set, but it is large enough to fix a well defined point on the stress-diagram. 
A very extended experience in its application, therefore, serves but to con¬ 
firm the author in its continued use, and in the recommendation of its gen¬ 
eral adoption which is here put forth for the first time. * 

^ 14. The Ultimate Strength of a specimen subjected to tensile stress is 

measured by the maximum load carried, and is indicated on the stress- 
diagram by the true maximum point in that curve. It is found by dividing 
the maximum breaking load by the original area of cross-section. In case 
of the more plastic metals, the area of the broken section is usually about 
one half the original area, so that the ultimate strength of the actual section 
at rupture when found by dividing the breaking load by the final area of 
this section would be about twice the ultimate strength as computed on the 
original section. That is to say, the drawing down and pulling out of the 
metal has nearly doubled its strength per scpiare inch. The term “ultimate 
strength ” however , always refers to the original section, and is found by 
dividing the maximum load by the original section. 

~ 15. The Percentage of Elongation is found by dividing the increase of 
length after rupture has occurred, by the original length. By original 
length is meant a certain portion of the specimen which has been reduced 
to a uniform cross-section before testing. A standard length for tensile- 
test specimens in America and in England is eight inches, while in 
Germany and France it is twenty centimeters, these standard lengths being 
practically identical. The elongation of a test specimen of the plastic 
metals may be divided into two portions: (a) that part of the elongation 
which is uniformly distributed over the section; (b) that part of the 
elongation which occurs in the vicinity of the section which finally breaks. 
Thus in Fig. 10 are shown four sets of test specimens of mild steel, there 
being three specimens in each set. All the specimens of one set were 
originally of the length indicated by the untested specimen which stands 
on the left side of each group. The specimen next adjoining it on the 
right has been stretched to the limit of the elongation indicated in (a) 
above, or until there is an indication of a local reduction of area. The 
right-hand specimen in each group shows the local elongation and reduc¬ 
tion, but the specimen has been removed from the testing-machine before 
rupture occurred. The middle specimen of each group has been tested to 
the ultimate strength of the material, since, when the specimen begins to 
reduce locally, the ultimate strength has been passed, and the strain-diagram 
begins to fall, or it is developed under a diminishing load. 

By the amount, therefore, that the right-hand specimen in each of these 
groups is longer than the middle specimen of the group, by so much has 
the length been increased by the local drawing out on the section where 
failure will finally occur. The first elongation, therefore, is that portion 
which is uniformly distributed over the specimen, and the second is that 


* See also Arts. 261, 262, and 263, pages 306-311. 





Fig. 10.—Showing the Necking-down Action of Steel Bars before Rupture. (Tetmajer, vol. iv.) 


22 


THE MATERIALS OF CONSTRUCTION. 



























MATERIALS UNDER TENSILE STRESS. 


23 


which is concentrated in the vicinity of the final failure. Both of these 
elongations are, however, measured and included in the total elongation, 
from which the percentage of elongation is determined. The total elonga¬ 
tion is obtained after rupture has occurred, by placing the two ends together 
and measuring the distance between the primitive gauge-marks. In the 
case of specimens having shoulders at their ends the gauge-marks should 
be at least one-half inch inside of the shoulder, since the metal adjacent to 
the shoulder does not elongate fully, because of the strengthening effect 
of the enlarged cross-sections at the ends. 

It will at once be apparent from a study of these specimens that the 
(b) elongation, or that which is locally developed in the vicinity of final 
rupture, is nearly the same in all these specimens; whereas the ( a ) elonga¬ 
tion, or that which is uniformly distributed over the specimen, is always 
directly proportional to the length. The total elongation, therefore, will 
not be proportional to the length. In other words, the percentage of total 
elongation will be greater for the short specimen than for the long ones. 
This shows the necessity of using standard lengths of these specimens when 
the percentage of elongation is to be found. 

The percentage of elongation is the result which indicates the ductility 
of the material, this being one of the most important qualities of the 
metals used in structural designing. 

16. The Reduction of Area of Cross-section is found by determining the 
area of the broken cross-section, subtracting this from the original area of 
cross-section, and dividing the difference by the original area. This is not 
so important an indication or result as the others described above, but it is 
customarv to determine it, and to add it to the record. For the ductile 

4/ 

metals this reduction of area may be as much as from fifty to sixty per cent 
of the original cross-section. 


CHAPTER III. 


MATERIALS UNDER COMPRESSIVE STRESS. 

17. Two Classes of Engineering Materials. —Engineering materials may 
be divided into two general classes, according to their manner of failure in 
compression. 

Plastic or viscous materials are those which will flow without showing 
any other indication of failure under a sufficient compressive load. 

Brittle or comminnible materials are those which will crush to a pow¬ 
der, or crumble to pieces, or fail by shearing on definite angles under a 
compressive load. 

In the former class are such materials as wrought iron, soft and medium 
steel, the alloys, lead, copper, zinc, and the like. Of the latter class are cast 
iron, hard or tempered steel, brick, stone, cement, etc. The laws of failure 
of these two classes are very different, and they will, therefore, have to be 
discussed separately. 

18. Crushing Strength of Plastic or Viscous Materials. —There is no 
such thing as an “ ultimate strength” in compression of a plastic body. 
There is, however, a definite “apparent elastic limit,” the same as in ten¬ 
sion. Beyond this limit the material simply spreads, and increases the area 
of its cross-section indefinitely under an increasing load, as shown in Plate 
II. The elastic limit in compression of such a material is the greatest load 
from which the specimen will fully recover, or it is the greatest load within 
which the stress and deformation bear a constant ratio to each other. This 
elastic limit in compression for wrought iron and steel is, fortunately, 
about the same in pounds per square inch as the elastic limit in tension. 
It is not customary, therefore, to test such materials in compression, but 
to assume that they have the same elastic limit in compression which they 
are found to have in tension. 

19. The Law Governing the Strength in Compression of a Brittle or Com- 
minuible Material. —Experiments show that all such materials when sub¬ 
jected to a compressive load fail by shearing on certain definite angles. 
The resistance to movement along these angles is made up of two parts: 
first, the strength of the material to resist shearing; and second, the 
frictional resistance to motion along this plane. The sum of these two 
resistances must equal the shearing component of the load imposed when 

24 


PLATE II, 



Wrought Iron. 


Steel. 



Wrought Iron. 


Steel. 






Relative Malleability of Wrought Iron and Soft Steel. 

All the specimens were originally of the shape of the one remaining undeformed. 
The wrought-iron specimens uniformly show large cracks. (From von Tetmajer’s Com¬ 
munications, vol. iv, PI. V.) 
























MATERIALS UNDER COMPRESSIVE STRESS. 


25 


resolved along the shearing plane. To find what this angle should he. we 
may equate the two resistances here described with the shear¬ 
ing force, and find the angle of rupture, the determining 
condition being that this angle shall be that which offers the 
least total resistance to failure under a crushing: load. This 
angle may be found in the following manner: 

Let s = shearing strength of the material per square inch; 

A — area of prism = 1 square inch; 

6 — angle of rupture; 
p = crushing load per square inch. 

The tendency to slide on the plane of rupture is p sin 6. 

The resistance to sliding is s sec 6 -f- fp cos 6, where /is 
the coefficient of friction = tan 0, where 0 = angle of re¬ 
pose. Hence, at failure, 

p sin 6 = s sec 6 -j - fp cos 6 .(1) 

It is evident that the angle of rupture will be such as to cause failure 
under the least load; hence if 6 be taken as the independent variable, we 
shall have at rupture 



( j^ = — s( cos’ 6 — sin 2 6 -f- 2f sin 6 cos 6) = 0, 


or 


sin 


2 6 


__ cos 2 6 
•' 2 sin 6 cos 6 


cos 20 
sin 26 


= — cot 26. 


( 2 ). 


Whence, since/ = tan 0, we have 

tan 0 ^ — cot 2 6— — tan (90° — 26) — tan (20 — 90°), 


or 


0 = 2(9-90° and ft = ^±1 = 45 ° + %. ... (3) 


That is to say, the angle of rupture is 45° plus one half the angle of repose. 
If the friction had been omitted, we should have had 

p sin e - s sec 0; whence = - s(cos* 0 - sin 1 ff) = 0; 

1 — 2 sin 2 6 = 0; 2 sin 2 6 = 1, or 6 = 45 . . . • (H 

It has been cus* v y to neglect the friction, and to state that the 

planes of rupture r ako iis angle of 45° with the horizontal;* but Lie 
actual plane of rupture, when the specimen has sufficient height, is ab< 

' * Coulomb is responsible for this theory, while Namer lias given the true aiui'ysib 

Most writers, including Rankine, have followed Coulomb, however. 

















26 


THE MATERIALS OF CONSTRUCTION. 


55° with the horizontal, or 35° from the direction of the applied load. See 
Figs. 12 and 13, showing tests on sandstone made by Prof. Bauschinger.) 
Mr. Charles Bouton has shown* that the theoretical angle of rupture is 



Fig. 12.—Bauscliinger’s Compression Tests on Sandstone. 


borne out in practice with many kinds of materials. (See Fig. 14 for 
photographic views of crushed specimens of cast-iron cylinders of various 
heights, showing angle of rupture.) 

The following table gives the results of Mr. Bouton’s determinations of 
the theoretical and the actual values of this angle: 

* In a thesis for the degree M.S. at Washington University, 1891, entitled Theory 
and Experiments on the Laics of Crushing Strength of Short Prisms. Mr Bouton also de- 
l rod the for ulae in this article and afterwards found that Navier had anticipated him. 





















MATERIALS UNDER COMPRESSIVE STRESS, 


27 


Material. 

Number 

of 

Experi¬ 

ments. 

Observed 

Angle 

of Rupture. 

0 

Observed 
Angle 
of Repose. 

<t> 

Theoretical 
Angle 
of Rupture. 

4> 

Differences. 

** F.” cast iron. 

24 

54°.8 ± 0°.2 

20°.6 

55°. 3 

- 0° .5 

“ C5 W ” rust iron.. . . . 

24 

55 0 + 0 2 

16 9 

53 4 

+ 1.6 

Tamest one. 

4 

62.2 

33 4 

61 .7 

+ 0.5 

Asphalt paving mixture 

3 

59.7 

27 .3 

58 .6 

+ 1 .1 

Milwaukee brick. 

4 

58.2 

27 .0 

58 .5 

- 0 .3 















































28 


THE MATERIALS OF CONSTRUCTION. 


The “ F.” cast iron was good foundry iron, having a tensile strength of 
22,000 pounds per square inch and a modulus of elasticity of 14,500,000; 
the “ C. W.” iron was car-wheel iron, having a tensile strength of 20,000 


rrr 



Fig. 14. —Bouton’s Compression Tests on Cast Iron. 

pounds per square inch and a modulus of elasticity of 6,500,000, or less 
than one half of the former. 

20. Relation of Crushing Strength to Shearing Strength. —To show the 
relation of the crushing strength to the shearing strength, we have, from 
equation (1) in the previous article, 


s = p(s\n 0 cos 6 — / cos 2 6) ; 


also, from equation (2), 

f — — cot 20 — 

4 ' 


cos 20 _ cos 2 6 — sin 2 0 
sin 2 0 ~ 2 sin 6 cos 0 ' 


Substituting this value of /, we find 










MATERIALS UNDER COMPRESSIVE STRESS. 


29 


or 

p ~ 2 s tan 6, .(6) 

where t — compressive strength in pounds per square inch, and 
s = shearing strength in pounds per square inch. 

This relation was also shown by Mr. Bouton to be well borne out in 
practice. The great trouble to prove such a relation is to find s experi¬ 
mentally on brittle materials without introducing bending stresses. (See 
Arc. 37.) 

21. Relation of Crushing Strength to Relative Dimensions of Specimen.— 

This is a very important matter. Hitherto nearly all crushing-test speci¬ 
mens of brittle materials have had a cubical form. So long as the theoreti¬ 
cal angle of rupture was thought to be 45° this was proper; but since this 
theoretical angle approaches 60°, it is evident that the height of the speci¬ 
men should be at least one and one half times the least lateral dimension, 
in order to allow of failure on a normal angle. Prof. Bauschinger has 
studied this question very exhaustively, and the following conclusions are 
drawn from studies of his results of tests on a very uniform quality of fine 
Swiss sandstone, all possible refinements as to appliances having been 
introduced: * 

He recommends the formula 




for all shapes of cross-section and for all relative heights, where 

p — crushing strength per unit of area; 

A = area of cross-section; 
u — perimeter of cross-section; 
h = height of specimen; 
a and b = constants. 

For rectangular cross-sections the following formula serves very well: 

VA 

p = k+k'-f, .. (8) 


where Jc and h f are constants. 

The application of this formula is shown in Fig. 15, in which the tests were 
on three sets of sandstone prisms of the dimensions 2| in. by 5 in., 3f in. 
by 5 in., and 5 in. by 5 in. in cross-section, respectively, the heights of each 
set varying from one-half to five times the least lateral dimension. It is 

*Mittheilungen aus dem Mechaniseh Technischen Laboratorium der K. Techmschen 
Eochscliule in Munchen , von J. Bauschinger, vol. vi, 1876. 













30 


THE MATERIALS OF CONSTRUCTION ,. 



Fig. 15. —Relation between Crushing Strength per square inch and Ratio of Cross- 
section to Height of Specimen. (Bauschiuger.) 


/0000 

mo 

oooo 

7000 

oooo 

sooo 

0 04 as /£ /2 22? 2.4 2.8 22 22 4.0 4.4 4.8 2.2 22 0.0 

Fig. 16.— Relation between the Crushing Strength per square inch and the Ratio of 
Height to Least Lateral Dimension. (Bauschiuger and Bouton.) 



















































































MATERIALS UNDER COMPRESSIVE STRESS. 31 


evident that formula (8) fits the results very well, the equation of the full 
line being 


p = 5G00 -f 1400 


Va 

IT 


in pounds per square inch. 

If a simpler formula is desired, the following may be chosen: 



P — k + kl. 


( 10 ) 


where £q = least lateral dimension. 

Fig. 16 shows how well this law fits the observations, the equation for 
this locus being, for the tests on sandstone, 

5500 + 1565- 1 .(11) 

/ b 


The lower curve in Fig. 16 represents the law for sandstone prisms, and 
the upper one the law for cast-iron cylinders, when the strength argument 
on the diagram is multiplied by ten. The experiments for the former were 
made by Prof. Bauschinger, for the latter by Mr. Bouton. Mr. Bouton 
made his tests on two kinds of cast iron, using five bars of each and 
turning from these ten bars nearly one hundred cylinders. The tests on 
the longer cylinders have been excluded from the results plotted, as their 
length caused them to bend greatly, and hence their failure did not follow 
the law for short prisms. The plotted points on the tests of cast iron 
represent the average results of the number of similarly proportioned 
cylinders. In these tests there seems to be a possible minimum point at 

about ~ = 1.5, this being about the height which equals tan 6, or the least 

Lb 

height offering an opportunity for failure on the theoretical angle. Why 
this should be the case does not appear, and the mean curve has been drawn 
without showing such a minimum indication. 

22. Relative Strength of Prisms and Cubes. —In order to show the 
relation of the strength of a prism to that of a cube BauschingePs observa¬ 
tions were used, as plotted in Fig. 16 to p and and the curve as shown 
in Fig. 17 is the result.* 

Thus, from this mean curve, we have the equation 




strength of prism 
strength of cube 


= 0.778 + 0 


000^1 
Aj Aj Aj -m • 

h 



where l\ — least lateral dimension, and h — height of prism. 

This equation shows that the strength of a stone prism whose height is 


* This law holds between the limits h = 0.4& and h = 5 b, these being the limits of 
the observations. 









32 


THE MATERIALS OF CONSTRUCTION. 


one and one half times its least lateral dimension has a strength equal to 
92$ of the strength of a cube of the same material. 

7 g 

This height of — = — was found to be necessary to allow the material 

I ), 2 


to shear on the theoretical angle of 45° -j- Hence when the cubical 

'form is used for test specimens in crushing, the results are 9$ greater than 
if the proper height of specimen had been chosen. 



my mmf/j mi/fs 

22222-S2C7/0M 2/2M. x £w\s/f/Y0ST0/9£ 

5 "» x S"« J ( m/v/ ^) — 
(2221/2) 


2.7 


% W /2 2222/222 22 12262122222 / 


ff/ 


W2wm= f 


I ? 0.4 68 48 4.6 £6 34 £8 < 3.2 36 40 4.4 4.3 3.3 6.6 6.0 

% 

Fig. 17. — Relation between the Crushing Strength of Prisms and Cubes. 


Also, if a brick, for instance, be tested flatwise, in which position 
^ = 2, we find from this curve it will give a result 22$ greater than that 

ft 

b 2 

for a cube, and 33$ greater than that for a specimen in which f = — In 

n o 

other words, the results from tests on cubes are 9$ too large, and on bricks 
flatwise they are 33$ too large. 

It will also be noted that, so far as these tests go, ilie unit strength of 
the material is no function of the size of the specimen, but only a function 
of its form. 

23. Effects of Loading a Portion of the Cross-section.* — {a) Chamfered 
Edges .—If the edges of a cube or prism be chamfered off as shown in 
Fig. 18, and the load applied uniformly over the reduced area, the law of 


* All the tests discussed in this article are taken from Prof. Bauschinger’s published 
repor ts, but the author of this work has discussed them with the results as given. 











































MATERIALS UNDER COMPRESSIVE STRESS. 


33 


the variation of strength with varying areas of compressed surface is 
shown by the curves on this figure. 

Thus, as the area of pressed surface approaches that of the full cross- 
section, the load carried per unit of pressed surface decreases, as shown by 
the curved locus at the top, while the average load on the full cross-section 



Fig. 18.— Crushing Streugtli of Cubes with Chamfered Edges. (Bauschinger.) 


increases uniformly, as shown by the straight locus of Fig. 18, the two loci 
meeting at 9500 pounds, the strength per square inch of a full cube. 

These results show clearly that the bearing surface should be that of 
the full cross-section of the specimen if normal results are to be obtained. 
The contrary has sometimes been asserted—that the strength of the 
specimen was not increased appreciably by the material outside the bearing 
surface. In other words, crushing-test specimens should he true prisms in 
form , without chamfered edges or rounded corners. 

Since the locus of unit strength for bearing surface, Fig. 18, comes 
nearly into a horizontal direction as the pressed surface approaches the full 
area of cross-section, it follows that when the pressed surface is nearly 
equal to that of the full cross-section of the specimen the error introduced 



































34 


THE MATERIALS OF CONSTRUCTION. 


by considering only the pressed surface is very small. For instance, if the 
area of the compressed surface is 0.8 that of the full cross-section (dimen¬ 
sions of cross-section 0.9 those of the full section), the error introduced by 
considering the pressed surface only would be by this curve = 3.2$. 

(b) Square Bearing, Symmetrically Placed .—When the pressed surface 
is square and placed symmetrically on a larger cube, the relation of the 
resistance per unit of pressed surface to the strength of the cube is shown 
on Fig. 19. Here the curves are given for the small bearing on one side 



Fig. 19.—Effect of Loading a Portion only of the Surface of a Cube. (Bauschinger.) 


and also on opposite sides, and the crushing resistance computed and 
plotted per unit of bearing surface and also per unit of cross-section of the 
cube. Evidently the loci must all meet at a point where the bearing area 
equals the total area on each side, and this point will be the strength of a 
cube of this material, which was 9500 pounds per square inch, the same as 
shown in Fig. 18, the material being the same. 

















































35 


MATERIALS UNDER COMPRESSIVE STRESS. 

( c) Bearing Surface Rectangular and Extending Entirely Across the 
Cube .—In this case the resistance per square inch is a function of the dis¬ 
tance of the pressed surface from the edge of the cube. This law is shown 
in Fig. 20. The material being the same as before, the strength of a cube 



Fig. 20.—Elfect of Loading a Zone on the Surface of a Cube. (Banscliinger.) 

would be 9500 pounds per square inch. This corresponds to a distance 
from the edge of the cube equal to 8$ of the half-width. As the bearing 
surface had a width equal to 10# of the half-width of the specimen, it fol¬ 
lows that the outer line of the pressed surface came within 3# of the half¬ 
width, or 14# of the total width from the edge of the specimen when the 
normal strength of the material was developed.* 

24. General Laws of Crushing Strength.—The laws of crushing strength 
shown in Figs. 15 to 20 apply specifically to a particular quality of sand¬ 
stone. In Fig. 1G it is shown that cast iron follows a different law. In all 
probability each kind of material, or at least materials which have different 
angles of rupture (that is to say, different coefficients of friction), will show 
different curves for the several relations indicated in these plates. In the 
absence of any more definite information, however, on this subject, it is. 
thought the curves shown upon these plates will serve to indicate in a 
general way the laws of the variation of crushing strength with the varying 
conditions here indicated^ 


♦ See figures 12 and 13 for methods of failure for cases (a), (b), and ( c ). 









































36 


TEE MATERIALS OF CONSTRUCTION. 


By referring to Fig. 14 'it .will be observed that the cylinders all 
swelled more or less in the middle before rupture occurred. This is doubt¬ 
less due to the restraining action of the friction against lateral motion on 
the end bearing surfaces. It is difficult to take this source of strength 
fully into account in a theoretical analysis of resistance to crushing. 

25. Strength of Columns. —When a compression member is so long as 
to fail in compression by lateral deflection, its failure is a function of the 
'elastic-limit strength and of the stiffness (modulus of elasticity) of the 
material, rather than of the ultimate strength of the material in compres¬ 
sion. The discussion of this case properly comes in works on mechanics 
and on framed structures. The author has fully expressed his views on this 
question in his work on Modern Framed Structures , and to some extent in 
Chapter XVI of this work, and hence he will not occupy space with it here. 

26. Weakening Effects of Eccentric Leading. —Few persons are aware 
of the great increase of stress on the near side of a member subjected to a 


z 7 


V 




>as 

i 
i 

\ 
i 
i 
i 


A 


Z 7 





A 



direct stress (either tension or compres¬ 
sion) caused by an eccentricity of the 
load-line with reference to the gravity- 
axis of the member. This eccentricity 
may result from an eccentric imposi¬ 
tion of the load itself; or from the 
member being bent; or from the ad¬ 
dition of material on one side of the 
member, such addition usually prov¬ 
ing a source of weakness instead of 
strength. These three cases are shown 
in Fig. 21. In each case we have 

Total load = P ; 

“ area = A; 

Eccentricity = a; 

Width —Zi\ 

Moment of inertia of section = /; 

Radius of gyration of section = r,; 

Distance of extreme fibre from the 

gravity-axis = y x = with symmetrical 


sections; 

Total stress on nearest outer fibre = /. 


h 


Hence we have for symmetrical cross-sections, where ?/, = —, 

2 


r— P \ P ( a]l \ \ a]l \ ■ 

f -A + AW]=A\ l + ^y 


(13) 


* The stress due to the bending moment Pa is found from the equation m = H or 
/ = —p, where m — Pa, and I = Ar 2 . 


































MATERIALS UNDER COMPRESSIVE STRESS. 


3? 


1 IP 

For solid rectangular cross-sections we’ have r 3 = — = —; lienee for 


such sections 


P 


6 ^ 


f ~A l + - 


h 


(14) 


The proportionate increase in the stress , therefore , over that which 

would obtain for a concentric load is given by the fraction y. In other 

words, when a = ^h the stress on the outer fibre on the near side is doubled, 
compared with that for a central loading. 

To discover the weakening effect of additional material added to one 
side of a member, assume a central loading on a straight symmetrical 
member having an initial width = h, (a = o). If additional material, to a 
thickness of x, be now added on one side of this member, the new total width 

becomes h + x 3 and the eccentricity is a — —. Assuming the member to be 


solid rectangular in cross-section, with original dimensions of b and h, the 
new dimensions of section are b and h-fx\ the former area was A — bh, and 


p p 

the latter A f = b(h 4- x). Before the addition we should have f — — = jt* 

v 7 J A bli 

After the addition we should have, from (14), for the stress on the 

near side, 



P 

b(h + x) 



_3z_\ 
li + x)' 


(15) 


Hence the increase of the stress due to an unsymmetrical addition of 
material is 

f‘ = f ~f = v(v+* + (V+zr _ a). (16 * 

This is zero for x = 0 and for x = 2 h, and it is a maximum for x = 

t 

when it becomes 

max. fi [tor x = |) = ~ ^ = if. .(11) 

Hence we may say that the addition of material on one side of a mem~ 
her subjected to a direct stress symmetrically placed weakens it until the 
added material has exceeded twice the original thickness of the member, the 
maximum weakening occurring when the added material is one half the 
original thickness, when the enlarged member is only three fourths as 
strong as the original member .* 

* Attention was called to this fact by Mr. Carl G. Barth in Trans. Engrs. Club of 
Plata., Oct. 1891, p. 307. 










CHAPTER IV. 

« 

MATERIALS UNDER SHEARING STRESS. 

27. Two Manifestations of Shearing Stress. —When all the opposing 
external forces which act on a body lie in one plane,* but not in one and 
the same line, the resisting stresses are those of simple shear and cross¬ 
bending, without torsional stress. 

When the opposing external forces do not lie in one plane the resisting 
stresses are those of torsional shear, with or without cross-bending and 

i 

•simple shear. 

In any case these three kinds of stress are determined separately, as 
follows: 

(a) For Parallel External Forces in One Plane. —The moment of 
resistance of the bending (direct) stresses at any transverse section is equal 
to the algebraic sum of the moments of tho external forces on either side of 
that section taken about the neutral axis in that section. 

The simple shearing stress on any section is equal to the algebraic sum 
of the transverse components of the external forces on either side of that 
•section. 

(b) For Parallel External Forces Not in One Plane. —First replace all 
the forces by equal parallel forces acting in the plane of the axis of the body, 
and by couples equal in value in each case to the force multiplied by 
its displacement. Then the moments of resistance and the simple shearing 
stresses will be the same as in the last case, and in addition there will be 
the moment of torsion. 

The torsional moment at any transverse section is equal to the algebraic 
sum of the moments of the couples of the displaced forces, acting on either 
■side of the transverse section in question. 

(c) For Non-parallel Forces Acting in Any Manner. —Resolve all forces 
into horizontal and vertical components at their points of application, and 
then solve for bending moments, shears, and torsions at any section in these 
two planes. 

The bending moment at this section will then be the square root of the 
sum of the squares of the bending moments at right angles to each other. 

* When a force is distributed over an area it is here supposed to act at the centre 
of gravity of these force-elements. 


38 




MATERIALS UNDER SHEARING STRESS. 


39 


The total shear will also be the square root of the sum of the squares of 
the primary shears at right angles to each other. 

The total moment of torsion will be the algebraic sum of the two 
moments of torsion found from the two sets of forces. 

28. The Moment of Torsion gives rise to a shearing stress over the entire 
cross-section, which is zero at the centre of gravity of the section, and 
which increases in intensity directly as the radial distance from the gravity 
axis. 


For various forms of sections, the following intensities of shearing stress 
are found, by the principles of mechanics, for the corresponding forms of 
cross-section. 


The general equation for resistance to torsion is 


31 = 




Figure. 

Dimensions. 

1 

Area. 

J* 

r 

J 

r 

7 

Radius — r . 

> 

ITT 2 

nr 4 

IT 

r 

nr 3 
~2~ 

O 

Outer radius = r l 

Inner “ = r x j. 

7r (}' 2 — ?'j 2 ) 

n (r 4 — ?- x 4 ) 

2 

r 

n(r 4 - r x 4 ) 

2 r 


m 

mil 


Side — b . 

ft 2 

b 4 

G 

i* 

b 3 

3 Vi 


wm 

\rm, 

i 


Outer dimension = b ) 
Inner “ = b x j 

ft 2 - 6 X 2 

b 4 - 6 j 4 

6 

2 ^ 2 

b 4 - V 

3 Vi 



# 

Side — a. .. 

3a 2 _ 

— F3 

ba 4 4 r- 
8 

a 

1.082a 3 

• 


Radius of circumscribed 
circle — r . 

2r 2 

r*(l + 2 Vi) 

r 

1.276? -3 




Longer axis = 2a | 

Shorter axis = 2b f. 

nab 

*-(a 3 6 -f- b 3 a) 

a 

~W + b*) 

0 

Longersemi-axes=a&a x » 
Shorter “ “ = 6&6 X ) 

n^ab—a^V 

n _[~ a6(a 2 +6 2 ) 1 

4 L-a 1 6 1 (a 1 2 +6 1 2 )J 

a 

n r 6(a 2 -f6 2 ) - 

r -^ i (a 1 2 +6 1 2 ) 
































































































40 


THE MATERIALS OF CONSTRUCTION. 


where M — total torsional moment; 

$ = shearing stress on extreme fibre; 

J* = polar moment of inertia of cross-section about the gravity axis; 
r = distance from neutral axis to the extreme fibre having the 
shearing stress s. 

Whence we have, for the forms figured, the relations given in the 
table. 

29. Shearing Deformations. —As shown in Arts. (7) and (8), a shearing- 
action of external forces results in angular deformation of the body. In 
the case of simple shear, or where the forces lie in one plane, the angular 
deformation from shear is very small, the bending being mostly due to the 
longitudinal deformations resulting in the direct tensile and compressive 

resisting stresses on the two sides of the 
neutral plane respectively. When the 
forces do not lie in one plane, or where 
there is a moment of torsion, the angular 
deformation gives rise to a twist of the 
body about the neutral longitudinal axis. 
Thus in Fig. 23 assume the solid cylinder, 
anchored at o, to have a length l and a 
radius r. Let the torsional moment be Pa — M t . Then the shearing 
stress on the extreme fibre is, by equation (1), 

M t r 2 Pa 



\ 




s = 


J 


7i r 


3 > 


0 ) 


where J is the polar moment of inertia = twice the rectangular moment of 
inertia in this case. 

In Art. 9 the shearing modulus of elasticity was defined as 

shearing stress per sq. in. 


E s = 


angular deformation 

If we take the stress and angular deformation of the outer fibre in 
Fig. 23, we have: 

2 Pa 


Shearing stress per sq. in. = s = 


711 


.3 


rd 


Tangent of the deformation angle — — = deformation angle, 

since this angle is small. 

Hence we have 

p _ 2 Pal _ si 

s ~ ~nr r 6 ~V6' . 


( 3 ) 


* The student’s attention is called to the fact that the polar moment of inertia is 
equal to the sum of the true rectangular moments of inertia about the principal axes 
through the centre of gravity of the section. 
























MATERIALS UNDER SHEARING STRESS. 


41 


2 Pal _ si 
nr*E s rE s ' 


In general, for any cross-section we have 





or 


M t l _ si 

* * 



where y x — distance from the neutral axis to the extreme fibre in which the 
stress is s. 

In Art. 9 it was shown that the shearing modulus of elasticity = $ of 
Young’s modulus, or E s — f E. Hence in terms of Young’s modulus of 
elasticity, which is that ordinarily given, we have 


^ _ 5 M t l _ 5 si 

~ 2 * EJ ~~ 2 'Ey l 



where 6 = angular movement in terms of the radius; 

M t = torsional moment on the bar; 

l — length of bar between sections representing a relative angular 
movement of 6; 

s = shearing stress on outer fibre; 

E s — shearing modulus of elasticity of the material; 

E — the ordinary modulus of elasticity; 

J — polar moment of inertia = I x + I yi where these^are the rectan¬ 
gular moments of inertia about the principal axis through the 
centre of gravity of the section; 

y x — distance from neutral axis of outer fibre in which the shearing 
stress is s. 










CHAPTER V. 

MATERIALS UNDER CROSS-BENDING STRESS. 


30. Historical Sketch.*—For two hundred and fifty years the true theory of the 
strength of a beam has been a much-mooted question amongst physicists, engineers, 
and mathematicians. 

Galileo was the first of whom we have any record who undertook to discuss the 
problem. In his famous Dialogues (Leiden, 1638, from which Fig. 24 is taken) he 



Fig. 24. 

propounds a theory based on an assumed absolute rigidity of the material, and con¬ 
cluded that the fibres of the beam were subjected to a uniform tension which acted 
about the base of the beam as a fulcrum. On this theory the moment of resistance 


*This historical review of the development of me irue tneory of the beam is derived 
mostly from Saint-Venant’s TIistorique Abrege des Recherches sur la Resistance et sur 
V Elasticity des Corps So tides, prefixed to his Navier’s “ Lecons,” Third Edition, Paris, 
1864, and from Todliunter’s History of the Theory of Elasticity, Cambridge, Eng., 
1886. It is here reprinted from the author’s joint work on Modern Framed Structures. 

42 





























































MATERIALS UNDER CROSS-BENDING STRESS. 


43 


•of a solid rectangular beam would be 


fbh' 



material in tension. 


where / is the ultimate strength of the 


Robert Hooke first published his famous law of the relation between deformation 
and stress in 1678, discovered by him he says 18 years previously, and kept secret for 
the purpose of procuring patents on some applications of the principle to springs for 
watches, clocks, etc. Two years previously he had ventured to publish the Jaw in 
an anagram at the end of another book, in this form, 4 " c i iiinosssttuv ,” whicli 
being interpreted reads, “Ut tensio sic vis ,” or, “as the extension so is the resist¬ 
ance.” Hooke makes this law apply to all “springy” bodies, amongst which he 
names nearly all ordinary solids. This is still known as Hooke's Law. 

Mariotte showed by experiment in 1680 that the fibres on one side of the beam 
were extended and on the other side compressed, and assumed that the neutral 
surface passes through the centre of gravity of the section. 

Varignon, in 1702, undertakes to harmonize the theories of Galileo and Mari¬ 
otte, by admitting the extension of the fibres, but puts the neutral plane at the bot¬ 
tom, as Galileo did, and assumes the tensile stress as uniformly varying from there 


to the other side. 


This w T ould make the strength of a solid rectangular beam 


fbld 


3 




which agrees almost exactly with the facts for cast iron at rupture when / is the 
tensile strength. 

James Bernouilli made an important advance by applying Mariotte’s law to 
obtain deflections of beams (1694 and 1705), and argued that the position of the 
neutral axis is a matter of indifference, which was a great error. He denied the 
truth of Hooke’s law, which we know is not applicable to all substances, nor to the 
point of rupture with any substance. He first constructed stress diagrams, but 
his work in the field of hydraulics was of even greater importance than in the study 
of solids. 

A. Parent , a French academician, seems to have been the first to perceive (1713) 
the mechanical necessity of equilibrium between the tensile and compressive stresses, 
which condition, together with that of a uniform variation of stress, fixes the posi¬ 
tion of the neutral axis at the centre of gravity of the section. This important dis¬ 
covery seems, however, to have passed unnoticed. 

Coulomb reannounced this relation in a memoir to the French Academy in 1773, 
or sixty years after its first publication by Parent. Saint-Venant credits Coulomb 
with never having seen Parent’s work, as no writer of that century has mentioned 
it. But even after this second publication of so important a necessary truth, such 
workers as Girard, Barlow, and Tredgold all misconceived the mathematical necessi¬ 
ties in the problem, and resorted to various makeshifts to explain the strength of 
beams. 

Navier finally, in 1824, put the matter on a solid mathematical basis, although 
he also at first went entirely astray. He stated in his first edition that the moment 
of resistance varied as the cube of the depth of the beam, and in his second edition 
this error was corrected, but the moment of the stresses on one side of the neutral 
axis was said to be equal to the moment of the stresses on the other side, about that 
axis, an equality which does not exist except on symmetrical sections. Navier also 
fully developed the theory of the deflection of beams as we now use it. 

Saint-Venant , a student of Navier’s, has finally (1857) in his notes on Navier’s 
Lemons given a complete analysis of both the elastic and the ultimate strength of a 
beam, with suitable equations which will give theoretical results agreeing with the 
actual tests, when the empirical constants are properly evaluated. This great engi¬ 
neer, physicist, and teacher has done more than any other one to bring theory and 
practice into harmony and to put both on a thoroughly scientific basis, so far as the 
strength and elasticity of engineering materials is concerned.* 


In spite of these various true expositions of this subject the source of 
strength in a beam continues still to be very imperfectly understood by 


* He died January 6, 1886. 






44 


the materials of construction. 


many engineers, and even by current writers on applied mechanics, and 
gross errors in this direction are still common. It is in consideration of 
this state of the science that the problem is treated so fully here. 

31. Fundamental Equations of Equilibrium.—When a solid body is in 
equilibrium under the action of non-concurrent external forces, the follow¬ 
ing propositions hold true for the body as a whole: 

I. The sum of the vertical components of the external forces is equal 
to zero. 

II. The sum of the horizontal components of the external forces taken in 
any plane is equal to zero. 

III. The sum of the moments of the external forces taken about any 
point is equal to zero. 

When a solid body is subjected to the action of non-concurrent forces 
acting in one plane the body may be regarded as a beam, since the effect of 
the external forces is to bend the body and develop in it what are commonly 

called cross-bending stresses. If a section 
be passed through the body perpendicular 
to the plane of the forces, and the portion 
of the body on one side of this section be 
removed,the other portion may beheld in 
equilibrium with the external forces act¬ 
ing upon it, by means of the stresses exist¬ 
ing in the body on this cross-section, these 
stresses now being regarded as external 
forces, as indicated in Fig. 25. Since the 
remaining portion of the body now under 
consideration is in equilibrium under the 
action of external forces and of internal 
stresses, which for the time may be re¬ 
garded as external forces, the three propositions given above will apply. 
Or, stating these propositions now so as to equate the real external forces 
with the internal stresses developed at the section, they would read as 
follows: 

If a transverse section be passed through a beam— 

I. The sum of the vertical components of the stresses acting at the sec¬ 
tion is equal to the sum of the vertical components of the external forces 
acting upon the body on either side of that section. 

II. The sum of the horizontal components of the stresses acting on the 
section is equal to the sum of the horizontal components of the external 
forces acting upon the body on either side of that section . 

III. The sum of the moments of the stresses acting on that section is 
equal to the sum of the moments of the external forces acting on the bodq on 
either side of that section. 

It follows from the above that if all the external forces acting upon 



Fig. 25. 

















MATERIALS UNDER CROSS-BENDING STRESS. 


45 


a beam are parallel vertical forces, the end reactions or supports being 
regarded as external forces the same as any primary weights or loads, and 
if no horizontal forces act upon the beam, then we should have for any ver¬ 
tical section— 

I. The shearing stress is equal to the algebraic sum of the external forces 
acting on either side of the section. 

II. The algebraic sum of the horizontal stresses acting on the section is 
equal to zero. 

III. The algebraic sum of the moments of the stresses acting on that 
section , which is commonly called the moment of resistance, is equal to the 
sum of the moments of the external forces about any point in that section. 

The effect of the action of cross-bending forces upon a beam is to bend 
or deflect it, thus shortening the lengths of the fibres or elements on the 
concave side of the beam, and lengthening them on the convex side. So 
long as this action does not exceed the elastic limits of the material, the re¬ 
sisting stresses are directly proportional to the deformations. Hence there 
is always found a compressive stress on the concave side and a tensile stress 
on the convex side of a beam, and therefore there will be a plane near the 
centre of the beam the elements of which are neither lengthened nor 
shortened, and on which there will be no longitudinal stress. This is 
called the neutral plane or “ neutral axis” of the beam. 

Furthermore, a geometrical effect of the bending of a beam is to pro¬ 
duce deformations which are zero at the neutral plane and which increase 
uniformly outward to the extreme convex and concave sides, and hence the 
longitudinal resisting stresses developed by these deformations also increase 
uniformly outward. Within the elastic limits, therefore, the direct stresses 
increase uniformly from the neutral plane to the extreme fibres. 

Since from Proposition II, as stated above, the summation of the hori¬ 
zontal stresses on the cross-section is zero, in simple cross-bending, where 
the external forces have no horizontal components, it follows that the total 
summation of the tensile stresses on the convex side of the neutral plane must 
always exactly equal the total summation of the compressive stresses on the 
concave side. Also by Proposition III the sum of the moments of all these 
stresses taken about any point in this plane must equal the sum of the 
moments of the external forces acting on either side of the section taken 
about the same point."} If this centre of moments be taken in the neutral 
plane itself it will at once be evident that the moment of the tensile forces 
on one side has the same sign as the moment of the compressive forces on 
the other side, and that they are, therefore, to be added together numer¬ 
ically in order to equal the algebraic sum of the moments of the external 
forces acting on either side of the section. While, therefore, the sum of the 
moments of the tensile stresses may be numerically equal to the sum of the 
moments of the compressive stresses (which is the case for symmetrical 
cross-sections), yet since they are to be added together numerically, in order 


46 


THE MATERIALS OF CONSTRUCTION. 


to equal or hold in equilibrium the moments of the external forces on one 
side of the section, there is evidently no mathematical necessity why the 
moments of the compressive stresses should equal the moments of the tensile 
stresses; and in unsymmetrical sections, and even in symmetrical sections 
beyond the elastic limit, these moments are not equal to each other. 

Since the stresses on any cross-section of a beam subjected to the action 
of bending forces increase uniformly from the neutral plane to the extreme 
sides, it is evident that it is only the stress found to exist in the extreme 
fibres or elements of the beam, which needs to be determined. That is to 
say, if the maximum stresses are kept within the working limits, it is imma¬ 
terial what the particular stresses are on other portions of the cross-section. 
It is common, therefore, to find the relation between the total moment of 
resistance of a beam (which of necessity is always numerically equal to the 
bending moment of the external forces), and the stresses on the extreme 
fibres or elements of the cross-section of the beam. This general relation 
between the bending moment and the stresses on the extreme fibres is made 
the subject of the following article. 

32. Relation between the Moment of Resistance and the Stress on the 
Extreme Fibre.—In Fig. 26 let the load F be applied at C, and this will 



produce a bending moment on AB of Pd. On this plane the moment of 
the longitudinal stresses makes up the moment of resistance which holds in 
equilibrium (and hence is always numerically equal to) the bending moment 
of the external forces. That is to say, M— Pd = M a , the moment of resist¬ 
ance. We shall here assume the cross-section to be irregular and unsym- 
metrical, as shown in the figure. The direct stress varies uniformly across 
the section in all cases. The following notation will be used : 

M — bending moment of the external forces. 

J/ 0 = moment of resistance of the direct stresses = M. 
p =■ intensity of the direct stress at the distance y from the neutral 
plane — ay, where a — intensity of direct stress at a unit's 
distance. 

f = intensity of the direct stress at the extreme side of the beam. 
y 1 — distance of extreme fibre on one side from the neutral axis. 
y* — “ “ “ “ “ the other side from the neutral axis. 

















MATERIALS UNDER CROSS-BENDING STRESS. 


47 


I = J* * y'dxdy = moment of inertia of the cross-section about the 
centre of gravity axis. 

y = distance from axis of reference to the centre of gravity of the 
cross-section. 

Intensity of stress on any fibre = p = ay; .(1) 

Total stress on fibre having an area of dxdy = j)dxdy = aydxdy; . . (2) 

Moment of stress on fibre dxdy = pydxdy — ay*dxdy; .(3) 

/ »+ V\ 

y'dxdy — al. . (4) 

-Vx # 

But as p — ay, so f — ay x and/' = ay/; or 


Therefore 


f /' 

a — — — — 

Vx v' 

M = M„ = al =C*-= Cl 

■ y, y. 


( 5 ) 


This is the general equation between the moment of resistance and the 
stress on either extreme fibre. When the section is symmetrical, y l = y/; 
hence f — f', and only one side need be considered. 

When the cross-section is solid and rectangular, equation (5) becomes 


M. = ifbh\ 


❖ 



The above demonstration assumed that the neutral axis or plane of the 
beam passed through the centre of gravity of the cross-section, since I was 
referred to this gravity axis. This remains to be proved. 

From equation (2) we have, the stress on any element is ay dxdy, where 
y is measured from the neutral axis. But for simple cross-bending the 
algebraic sum of these direct stresses over the whole section is zero; hence 
we have 

/ 

But 


4-^1 p+Vx 

ay dxdy — a ydxdy — a j yd A — 0.(?) 

V”-V\ U ~Vx 


j ydA = yA ,t 



fj 

*Both equation (5), M 0 = —, for any section, and equation (6), M 0 = \fbld, for solid 

V' 

rectangular section, should be thoroughly memorized by the student, as they are of con¬ 
stant application. _ 

f The symbol y denotes the distance from the axis of y to the centre of gravity of the 

fydxdy fydxdy 

cross-section, and it equals * 


[dxdy 


A 














48 


THE MATERIALS OF CONSTRUCTION. 


since the sum of the statical moments of the elementary areas about any 
axis is equal to the moment of the total area into the distance to its centre 
of gravity. Therefore we have, for reference to the neutral axis, 

/ Ay i _ 

ydA = 0, or yA — 0.(9) 

Vi' 

But yA can only equal zero when reference is made to the gravity axis* 
Therefore these two axes must coincide. In other words, the neutral plane 
always traverses the centre of gravity axis of the beam, so long as the 
stresses remain inside the elastic limits of the material in both tension 
and compression , and also provided the modulus of elasticity is the same 
for both hinds of stress. 

33. Moments of Resistance (Strength) of Beams of Various Forms of 
Cross-section.—The moment of resistance of a beam of any form of cross- 


Form of 
Cross-section. 




Distance of Centre 

Moment of Inertia 

Moment of Resistance 

of GraVity, 

about the 

in 

or Neutral Axis, 

Centre of Gravity 

Terms of the Stress 

from the 

of the 

in the 

Most Distant Fibre. 

Section. 

Most Distant Fibre. 

= Vi 

= 1 

= M 0 = f -- 



Vi 

h 

bh 3 


2 

12 

\f bk * 

d * 

nd i 

77 „ 

J 

~64 

W d3 

2, 

663 

1 

t 

IfT 

M fbh ’ 

h 

h* 

I 

2 VS 

12 

6 +2 _//i3 

h 

bh s - (6 - t')(h — 2f) 3 

663 _ (6 - t')(h - 2t) 3 f 

2 

12 

6 h 

i Ph* A t(b - t')(h — it) 

67i 3 — (6 — t')(h — t) 3 

fl 

Vh A t(b - V) 

3 ~ AVl 

Vi 

b A 26' h 

fta r36 + 6' (6+26'V-n 

/6+3(36 + 6')(6+6') „“1 

6 + 6' * 3 

L 12 18(6 +6')J 

6 L 2(6 + 26') -d>-f 26 )J 



































































MATERIALS UNDER CROSS-BENDING STRESS. 


49 


section was found to be, by equation (5), M 0 — y> where f = intensity of 

stress on the extreme fibre which lies at a distance from the neutral plane 
equal to y x , and /is the rectangular moment of inertia of the cross-section 
about the neutral or gravity axis. In the table on p. 48 are given the 
values of y x , I, and M 0 for various forms of sections which are commonly 
used as beams. For tabular and graphical methods of finding the moments 
of inertia of irregular forms, see Modern Framed Structures, pages 127-130. 

The values given in the above table are true for all values of/inside the 
elastic limit. When this limit is exceeded the stress no longer varies uni- 
formly across the section, but the stresses near the neutral axis are larger 
than the above theory allows, and hence, for a given actual stress on the 
extreme fibres beyond the elastic limit (as the breaking-stress, for instance), 
the moment of resistance is much more than would-be obtained by usinsr 
the breaking value of / (in tension or compression) and substituting this in 
the above formulas. It must be understood, therefore, that in no case are 
these formulce trite at rupture, hut only inside the elastic limits of the ma¬ 
terial. It is for this reason that the values of/as found from cross-bending 
tests carried to failure, and as computed from the above formulas, differ so 
largely from the breaking values of the material in direct tension or com¬ 
pression.* Thus, cast iron, which has a tensile strength of 20,000 pounds 
per square inch and which breaks on the tension side in cross-breaking, has 
a value of / when computed by the above formulas from a breaking-load, of 
from 30,000 to 40,000 pounds per square inch, depending somewhat on the 
shape of the cross-section of the specimen. The more the material is con¬ 
centrated near the neutral plane the more the value of / differs from the 
tensile strength. This value of / computed from the breaking moment, is 
called the modulus of rupture in cross-breaking. It is from 1.5 to 2 times 
the tensile strength of the metal. 

In timber beams the reverse is the case; that is to say, the crushing 
resistance being less than the tensile resistance, the modulus of rupture in 
cross-breaking is greater than the former and less than the latter, and it is 
in fact nearly a mean of the two. 

34. Strength (Moment of Resistance) of Beams beyond their Elastic Limits. 

—After the stress on the extreme fibres on one or both sides of the beam 
has passed the elastic limit, the distribution of ^stress over the section is no 
longer uniformly varying as was assumed in deriving the formulas of -the 
last article, and the law of this variation will now be examined. 

In all cases the variation of stress across the transverse section of a 
beam subjected to simple cross-bending, with or without shearing stress, 
follows the law of the variation of the stress ordinates to a stress-diagram 


* See a full discussion of this subject in the author’s work on Modern Framed 
Structures, Chapter VIII. 



50 


THE MATERIALS OF CONSTRUCTION. 


in which the extreme ordinate represents the stress on the extreme fibre of 
the beam. 

Thus in Fig. 28, suppose the beam to be cast iron, and to be bent until 
the stress on the extreme fibre on the tension side has become f t . Passing 



Fig. 28. 

now to the tension portion of the stress-diagram for this material,* we see' 
that this stress, f t , is found far beyond the elastic limit of the metal in ten¬ 
sion. Let us now recur to the fact that the deformation of the longitudinal 
fibres of the beam increases uniformly outward from the neutral axis, even 
beyond the elastic limit, since the section remains sensibly plane, and henco 
the uniform increase of the deformation is a geometrical necessity. In 
view of this fact it becomes evident that the law of increase of stress from 
the neutral axis outwards, or the law of the increments of stress correspond¬ 
ing to equal increments of deformation, is exactly that represented by the 
stress diagram, since here we have the increments of stress shown for equal 
increments of deformation. Hence it follows that if f t is the stress on the 
extreme fibre of the bent beam on the tension side the stresses on all 
other fibres on the tension side are truly indicated by the lengths of the 
corresponding ordinates on that side of the neutral axis, when the position 
of the stress ordinate f t in the stress-diagram is taken as the position of the 
extreme tension side of the beam, and the origin in that diagram is taken 
as lying on the neutral axis of the beam. Evidently the same argument 
would apply to the compression side. 

35. Distribution of Stress and Position of the Neutral Axis at Rupture. 
—In a brittle material like stone or cast iron, failure occurs on the tension 
side; while in the case of wood, failure usually occurs first-on the compres¬ 
sion side of the beam. The diagrams shown in Fig. 28 may fairly be taken 
as representing the facts in the case of cast iron, and those in Fig. 29 in the 
case of timber. Since timber is much stronger in tension than in compres¬ 
sion, it fails first on the compression side. Furthermore, after the fibres 
have buckled, or broken down, in compression, they are able to support only 
about three fourths as much of a load as before, so that the compression 
stress-diagram has the peculiar form shown in the accompanying figure. 

At failure, therefore, the tensile and compressive stresses are distributed 
over the section in a manner entirely different from that which obtains 


* See Chap. XXIII for complete stress-diagrams for cast iron of various qualities. 

















MATERIALS UNDER CROSS-BENDING STRESS. 


51 


within the elastic limit. The statement made in Art. 25, however, regard¬ 
ing the equality between the sums of the tensile and compressive stresses 
must still hold, as this is a mathematical or mechanical necessity; and as 
this total stress is graphically represented by the area of the stress-diagram 


c. 




shown on the sections of the beams in Figs. 28 and 29, it follows that these 
stress areas on the two sides of the neutral axis must he equal. 

Thus in the case of timber, for instance, the neutral plane at first lies in 
the centre of gravity of the cross-section, but after the material has begun to 
crush on the compression side, the neutral plane rapidly moves towards the 
tension side of the beam and often, at final rupture, it lies very near this side, 
the tension stress area being a triangle of very long base (stress on extreme 
fibre) and very short altitude (distance to neutral plane). It is evident 
that, although the beam has long since failed in compression, if it be con¬ 
tinuously deflected, failure must ultimately occur also in tension. When 
the material is weaker in tension than in compression such double failure 
cannot occur, since the tension failure parts the body, and the rupture is 
complete. Evidently no general law can be given for distribution of the 
stress across the section after the elastic limit has been passed, other than 
to say it is that of the corresponding stress-diagrams of that material in 
direct tension and compression respectively. 

36. Moduli of Rupture in Cross-breaking.—From the facts related in the 
preceding article it is evident that the formulae of Articles 32 and 33 cannot 
apply at rupture, and that if the breaking-load be used for computing the 
so-called ultimate strength of the material in pounds per square inch (the 
“ modulus of rupture in cross-breaking/’ and the quantity / in those 
formulae when P is the breaking-load, or when M is the ultimate bending 
moment), the result obtained as the value of / is a purely fictitious quantity, 
and that it does not really represent any actual tensile or compressive stress 
on the extreme fibres at all. It may, however, be called the “modulus of 
rupture in cross-breaking” in pounds per square inch, and used to indicate 
the strength of the material when loaded as a beam; but it must not be con¬ 
fused with, or assumed to have any fixed relation to, either the tensile or the 
compressive strength of the material. As a matter of fact it always lies 
somewhere between these two latter values, but it does not have any uni- 














52 


THE MATERIALS OF CONSTRUCTION. 


versal relation to them. It is always dependent largely on the form of the 
cross-section of the beam, as to the concentration of material near the neu¬ 
tral axis or near the extreme sides. Thus the elastic-limit strength of a 
rolled I beam can be very closely approximated by using for / in equation 
(5) the tensile or compressive elastic-limit strength of the material in either 
tension or compression, while the elastic-limit strength of a solid round 
bar could not be determined very closely by so doing. Also the ultimate 
strength of a cast-iron beam of an I-shaped cross-section could be deter¬ 
mined approximately by using the tensile strength of the material for the 
value of f on the tension side of the beam in eq. (5), but the ultimate 
strength of a round or square cast-iron bar would be nearly twice as much 
as would be shown by the use of eq. (5) if the tensile modulus of rupture 
were taken. 

37. The Distribution of Shearing Stress in a Beam.— (a) The Relation 
between Shear and Bending Moment at any Section. — In Fig. 30 assume 

any two adjacent sections dx apart. Let the total 
shearing force acting here be S. Call the bending 
moment at the first section M, and that at the other 
M'. Assume the beam to be cut at the section 
where the moment is M , and the left portion re¬ 
moved and replaced by the direct tensile and com¬ 
pression stresses, and also by the total shear, S. 
Then it is evident the moment at the adjacent 
section is 

M f — M -j- Sdx. . . . t (Id) 

But 



Fig. 30. 


M' - M = dM, 

hence we have 


M’ — M— dM— Sdx, or S =-^r*.(II) 

That is to say, the total shear on any transverse section of a beam is 
equal to the first differential coefficient of the bending moment. 

It follows from this that— 

(1) Where the bending moment is constant the shear is zero. 

(2) 11 here the shear is zero the bending moment is at a maximum 

or a minimum. 


{b) The Distribution of the Shearing Stress across any Transverse Sec • 
hon .—In Fig. 31 take two transverse sections, 
dx apart, as before, on which the moments are M 
and M f respectively. By eq. (5), Art. 26, we 
have for the stresses on the outer fibres at these 
two sections 

M V-. ^ M f ii 


f = 


I 



and /' = \ 

I 




























MATERIALS UNDER GROSS-BENDING STRESS. 


53 


Also for any horizontal section, as cc', the fibre stresses will be 


, y 

V =f~= 


y. i 


and p' 


M'y' 

T~- 


The breadth of the beam must be regarded as variable to obtain a gen¬ 
eral solution, and it will be denoted by b, a variable quantity. 

Now the total shearing stress on the section cc', whose area is b'dx, is the 
diffeience betw T een the total direct stress on a'c' and on ac. But the stress- 
on ac is 


fJ tpbihj= f v , bJ ¥- y - 

Similarly, the total direct stress on a'c' is 

fyuy = £ b EiD. 


The difference is 




b(M ' — M ) ydy _ j 1 bdMycly, 

r 1 ~ Jr 

But dM — Sclx by the previous article, hence we have at last 

Vl bSdxydy 


total stress on plane cc' = 


y' 


I 


.( 12 ) 


But the area of this section on cc' is b'dx . Hence the intensity of the 
stress on this plane is 


c/ y' 


l bSdxydv 
b'Idx 


Now S, /, and b’ are constant for any given beam, transverse section, and 
plane of shear cc'; hence these quantities can be removed from under the 
integral sign, and we have 

Intensity of shearing stress at any point in a beam, distant y' from the 
neutral axis, is 

S 

q ' = WD bydy . (13) 


Now J bydy is the statical moment of that portion of the cross-section 


of the beam outside the line cc' on which the shearing stress is obtained, 
taken about the neutral axis; hence we may say: 

The intensity of the shearing stress at any point in the cross-section of 
a beam is equal to the total shearing stress on that cross-section, multiplied 
by the statical moment of the area of that portion of the cross-section out¬ 
side the longitudinal plane of shear in question, about its axis in the neu- 












54 


THE MATERIALS OF CONSTRUCTION. 


tral plane , divided by the product of the moment of inertia of the entire 
cross-section into the breadth of the section at that point. 

This applies to solid sections of beams of all possible shapes. 

i'll l ^ 

For a solid rectangular section b is constant and / bydy — ^(y, 2 — £/ 2 ). 

tly ~ 

Hence for this case, where h = 2 y l9 and b — b' (a constant), we have 


6S 

bV 


'll 


, o 
w 


- y‘ 




(14) 


Hence the shear at the extreme sides, where y — is zero, and at the 
neutral axis 

q c 

.(15) 


3 £ 
q ° ~ 2 bit 


Beam uniformly loaded 



That is to say, the maximum intensity of the shearing stress on a solid 
rectangular section is f of the mean intensity. 

It is evident, also, that eq. (14) is the equation of a parabola with its 

vertex on the neutral axis, which 
is also the axis of the curve. On 
any particular longitudinal plane, 
also, the shearing intensity varies 
from end to end of the beam, as 
the total shearing stresses on the 
cross-sections vary, as shown in 
Fig. 32. By applying equation (13) to various forms of cross-section it can 
be shown that— 

1. The maximum shearing intensity in a beam of a solid rectangular 
section = f the mean shear. 

2. For a solid circular section it is f the mean shear. 

3. For I beams and plate girders it is practically equal* to the total shear 
divided by the area of the web portion alone.* 

38. To Dimension the Cross-section of a Beam.— (a) For Direct Stress on 
the Outer Fibre .—If the beam be of a solid rectangular form of cross-section, 

use eq. (6). If of any other form, use eq. (5) and evaluate — by the accom- 

y i 

panying table, if the form be one there given. If not, it will be necessary 
to compute the moment of inertia. If the form be irregular or unsym- 
metrical, it may be best to obtain the moment of inertia graphically.f In 
the case of unsymmetrical sections the neutral axis lies at different distances 
from the outer fibres on the tension and compression sides, and it may be 


necessary to compute both of them. Since f\ 


My . : 


/ 


, it is evident these 


* See Modern Framed Structures , Art. 130. 
f Ibid., Art. 127. 





















MATERIALS UNDER CROSS BENDING STRESS. 


55 


stresses per square inch are to each other directly as the distances of their 
fibres from the neutral axis. Thus in the case 
of a cast-iron beam the cross-section is made 
larger on the tension side, as in Fig. 33. Here 
the outer fibres on the compression side are 
much farther away from the neutral axis than 
the outer fibres on the tension side, and hence the maximum stress in com¬ 
pression is much greater than it is in tension, which is as it should be. 

For a solid rectangular section we have 




fbh' 
6 ’ 


or 


W = 


6M 

f 


( 16 ) 


Take M — maximum bending moment on the beam, in inch-pounds, 
■and /= working value of the stress on the outer fibre. This gives the 
value of bli 2 , and b and h can now be chosen at pleasure, conditioned on 
bh 2 being equal to the right-hand side of the equation. 

(5) For Shearing Stress along the Neutral Axis .—Since timber is very 
weak in shearing, as compared to its strength in tension and compression, 
timber beams and joists of ordinary lengths will usually fail by shearing, 
and hence they should be dimensioned to safely withstand this shearing 
action. Lanza shows* that the shearing strength of spruce and white- and 
yellow-pine beams is about -fo of the transverse modulus at rupture, but he 
recommends a much smaller factor of safety for shearing than for transverse 
rupture. If the factor of safety for shearing be two thirds that for trans¬ 
verse strength, we would have the working stress in shearing that in 
cross-breaking. In order to show what length of wooden beams would 
require dimensioning for shearing, using this relation of working stresses, 
we have 

f=Mq 0 .( 17 ) 


For a beam loaded at the centre 



and 



For a beam uniformly loaded 

If 


S — and M 


Wl 

8 * 


Also from (16), for cross-breaking, 




GM 

f 


and from (15) 


3 8 u 

* • = 2“ bh’ ° r M = 


3 W 

4 q ,' 


(18) 


* Applied Mechanics , 4th ed., p. 696. 


























THE MATERIALS OF CONSTRUCTION. 


50 


For a beam loaded at the centre 

bh' = G F= 3 N, .(is) 

J \T 

For a beam uniformly loaded 

.( 20 ) 

J 4 / 

From (17), (18), and (19) we find, for beams loaded at the centre, they 
are equally strong in shearing and in cross-breaking when 

i-ih .<*■> 

and for beams uniformly loaded they are equally strong in these two ways 
when 

y = —.(22) 

For shorter lengths wooden beams are weaker in shearing than in cross- 
breaking. Hence we have the following 


PROPOSITIONS. 

Wooden Beams in Shearing and Cross-breaking. 

I. For a centre load the beam should be dimensioned for a shearing 
stress when the ratio of length to height is less than one half the ratio of the 
cross-breaking to the shearing working stress. 

II. For a uniformly distributed load the beam should be dimensioned 
for a shearing stress when the ratio of length to height is less than the ratio 
of the cross-breaking to the shearing working stress. 

Thus, for white- and yellow-pine and spruce beams we may take 

f 

•- = 20 .* 

Whence 

All pine and spruce beams should be dimensioned for shearing failure: 



7 

For concentrated centre load when - ^ 10. 

h 


For uniformly distributed load when j “20. 



(24) 


in dimensioning for cross-breaking use equations (19) and (20), and 
for shearing use equation (18), for both concentrated and distributed loads. 
The following working values of/and q 0 may be used. 


* Here q a is not the true shearing resistance of sound timber, but the shearing resist¬ 
ance of large beams along their neutral axis, where they are usually season-checked. 














MATERIALS UNDER CROSS-BENDING STRESS. 


57 


Species. 

Working Values of 
Cross-breaking 
Modulus in Pounds 
per Square Inch. 

If) 

Working Values of 
Shearing Modulus in 
Pounds per Square 
Inch. 

(9o) 

White pine.. 

1000 

50 

Long-leaf Southern yellow pine 

1600 

80 

Short-leaf Southern yellow pine 

1400 

70 

Norway pine. 

1000 

50 

Spruce. 

1200 

60 

White oak. 

1200 

100 

Red cypress.. 

1200 

90 

Oregon fir. 

1000 

50 




Tables of working loads for beams of all these species of different lengths 
and depths are found in Chapter XXXII. 


DEFLECTION OF BEAMS. 



39. Development of General Formul®.—Let Fig. 34 represent that 
portion of a bent beam which is tangent to a horizontal line, the beam being 
bent under the action of vertical forces. Take the origin on the neutral 
axis where it becomes horizontal, in the section KL. Then any other 



section, as EC, distant x from KL, and originally parallel to it, now makes 
an angle with it which we will call i. These two planes would, therefore, 
intersect if prolonged, and the radius of the curve of the neutral axis 0A B 
will be called r. Evidently the position of the neutral axis in the plane EC 
is somewhat below the axis of abscissae, and the coordinate of this point A 
is now -f- x and — y, with reference to the origin 0. 

If we now draw the line GH parallel to KL, the intercepts in the outer 
fibres, between this section and EC, are the distortions of these fibres in 
the length OA — x. This distortion may be called a. 

To investigate the law of f he relative changes in x and y, take another 
section, FD, distant dx from EC. Then the coordinates of B with reference 
to A are -f dx and — dy, and the actual length along the neutral axis from 

A to B is ds = Vdx 2 -j- dy 1 . Also the angle between EC and FD is di. 





















58 


THE MATERIALS OF CONSTRUCTION. 


The angle i is also the angle the neutral axis at A forms with the hori¬ 
zontal, or 

. _ dy 

dx 


i = IF and di — .(22) 


But di is also equal to ^; 


1 _ d 2 y 
r ~ dxds' 


(23) 


Evidently, when the deflection angle i is small, dx is practically equal to ds, 
in which case dxds = dx 2 ; whence eq. (23) becomes 


1 _ d'y 

r dx 1 


(24) 


We also have CAH = GAB — i — 
the neutral axis to the outer fibre. 


, where ?/, is the distance from 
AE y 9 Jl 

Also 


._ x _ a ^ 1 _ a 

~ r~y J r~~ xy x 


(25) 


But from eq. (2), Chapter I, we have E — or a = In this case 

fx 

l = x, and p — f — stress on outer fibre; hence we have a — 

, fl fl 

Also from eq. (5) we have M 0 = *—, or y x = — . 

y i o 

Substituting these values of a and y x in eq. (25), and also M for M n , 
we obtain 

1 _ a _ fx 1 M M /0 ^ 

r~ xy x ~ E' x' fl~ El . { } 


Hence we have 


1 _ M _ dAy 
r~ El ~ dx 2 * 


(27) 


These are the fundamental equations for use in all problems in the 
deflection of beams.* 

The relation utilized to find deflection angles and movements is 

d 2 y _ M (dy\ _ Mdx 

ch? = ~¥r 0r “l dx) ~ ~El' 


* It is here assumed that the deflection is due wholly to the longitudinal deformation 
of the fibres from bending moment, and not at all from the action of the sheariug forces, 

which is substantially correct when ~ is large (see Art. 46). 















MATERIALS UNDER CROSS-BENDING STRESS. 


59 


That is to say, the change in the angle , or the amount of bending effected over 
a certain length of the beam, is equal to the holding moment into this length 
divided bg EL To find the total angle or total amount of bending in a given 
finite distance, therefore, where the bending moment is usually changing 
at all points, it is necessary to integrate, or sum up, the infinitesimal changes 
between certain limits or between certain transverse sections. Then having 
found the law of the curvature of the beam, the deflection, or vertical dis¬ 
placement at any point, can be found by integrating again from y' to y 
between the same transverse sections of the beam. The only difficulty in 
this work is encountered in finding the constants of the first integration. 
The following cases are the most common, in which both E and I are taken 
as constant throughout the length of the beam. Bending moment producing 
convexity downwards is called positive. 

40. Beam Fixed at One End and Loaded at the Other.—Here we have, 
for the value of the bending moment at any sec¬ 
tion x , M x = — P(l — x ); hence 


*.y = d l*y\ = a. = - 


dx 


\dxi 


= dx = 


P 

El 


(l — x)dx. 


Integrating this between the limits 0 and x , 
we have 

El 



du 

dx~ 1 ~ 


lx 


- !)• [+(7=0, since, for x = 0,^ = 0.] 

Integrating again from 0 to x, we have, dofloc O v y 

y = - [+0=0, since, for x = 0, y = 0.] 

To find the maximum angle, and also maximum deflection, make x = l, 
and obtain 

max. i = — —Jjr ;.(28) 


max. y 




2EI ’ 

PV 

ZEE 


(29) 


41. Beam Fixed at One End and Uniformly Loaded.—Let the load per 

unit of length — p. Then the bending moment 

. p(l — xf . 

at any section x is M x =- - ——; hence we 

have 



d 


Fig. 36. 


dx 


l = =di=- rj(V - Zlx + x')dx. 


\dx 


Integrating this from 0 to x, we have 

d l = i=- - to* + f-)- [+ O = 0, Since, for * = 0, = 0.] 
















60 


THE MATERIALS OF CONSTRUCTION. 


Integrating again from 0 to x, we obtain, as the deflection at any section,, 

y — --— + — V [ + C = 0, since, for x — 0, y = 0.] 

y 2 EI\ 2 3 ' 12/ L J 

Again, we find the maximum angle and deflection for x — l, where 


pi 3 

max. % — ~ 


QEI’ 


max. y = A = 


SET' 


( 30 ) 

( 31 ) 


42. Beam Supported at the Ends and Loaded at the Centre.—Let the 

_ L _ v load P be placed at the centre. 

Then the moment at any section is 


* -—_—*. jy 



_A-.-.---" 

2 1 

f 

c 

b 


Px 

M x = ~; hence we have 


Fig. 37. 

Integrating this from 0 to x , we have 

n T dy . Px 2 

EI dx = l = T 


nr dy .. Pxdx 
TjI — j— = di — 
dx 


2 


+ 0. 


Now (7 is the value of the angle i at the origin, where x = 0, or at the 
lower limit of the integration; in other words, C is the value of the angle 
we started with, and we must add to this, algebraically, the changes of the 
angle from 0 to x. To find the value of this constant we must pass to a 
point where the value of the angle is known. In this case we know this 

angle is zero for x — — m Hence make x = for which ^ = 0, and we 

fl £ (IX 


have C = — 


PI' 
16 * 


Therefore 


— _Pl' _P( > P\ 

EI . dx - 4 16 4 V 4 )• 


dy _ . _ Px* 
dx 1 ~ 
Integrating again, we have 
PIP 

4\3 4 


Ely = — l-j). [+(7=0, since, for x = 0, O — 0.] 


The maximum value of i is evidently at the ends, and of y at the centre. 
Hence we have 

PP 1 

16 EI . . 

PP 

4877 /. ' 6o > 


max. i = — 


max. y = A = 


* For this case the deflection due 


to shear is- 



(See Art. 46.) 























MATERIALS UNDER CROSS-BENDING STRESS. 61 


43. Beam Supported at the Ends and Uniformly Loaded.—Let the load 
per unit of length = p. Then the 

bending moment at any section x is * - - -- 







P 
2 El 


{lx — x*)dx. 



Fig. 38. 


Integrating once, we have 


dy_ 

dx 


p fix 2 
2EI\T 



As before, for x = j-, = 0; hence C =-• 

2 dx 2ffl\12/ 9 

dy _ . p fix 2 x * ? 3 \ 
dx~ l ~2EI\Z 3 12/ * 


Integrating again, we have 


y = 


p ( 

fix 3 

2 EE 

v 6 


x 1 _ / V 
12 12 / 


[+<7=0, since, for x = 0, y = 0.] 


I 


Max. i is found for x = 0, and max. y for x = -. Hence 

rj 


max. i — ~ 


pi 3 

24A7 

5 


max. y A . 


384 ’ El * 


• • • • • 


(34) 


(35) 


44. More Complicated Cases f are such as— 

(«) Beam supported at the ends and loaded at any point. 

(5) Fixed at one end and loaded in any manner. 

(c) Fixed at both ends and loaded in any manner. 

These and other cases are treated in works on Applied Mechanics, and 
they will not be further considered here. The difficulty in such cases is to 
evaluate the constants of integration. While this can always be done, the 
algebraic reductions are long and tedious. The following table gives all 
the results for the ordinary cases which are usually needed in practice. 

45. Table of Moments, Stresses, and Deflections of Beams having Con¬ 
stant Moments of Inertia. 


* For this case the deflection from shear is 


pi' 2 

8 E7A' 


(See Art. 46.) 


f For an excellent design of a home-made apparatus to be used in testing the correct¬ 
ness of all kinds of beam formulae, see a paper on this subject by Prof. James L. Green- 
leaf in Jour. Franklin Inst, for July 1895, vol. cxl. p. 27. 

















MOMENTS, STRESSES, AND DEFLECTION OF BEAMS. 


62 


THE MATERIALS OF CONSTRUCTION. 





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MATERIALS UNDER CROSS-BENDING STRESS. 


63 



















































































MOMENTS, STRESSES, AND DEFLECTION OF BEAMS. 


64 


THE MATERIALS OF CONSTRUCTION,. 


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MATERIALS UNDER CROSS-BENDING STRESS. 


65 






































































66 


THE MATERIALS OF CONSTRUCTION. 


46. Deflections from Shearing Forces.—For short beams it is necessary 

to take into account the shearing forces also. Since the modulus of 
elasticity in shearing is the ratio of the shearing stress to the angular 
distortion (transverse distortion per unit of length, since the angle is equal 
to its tangent), we may say that for a distance along the beam of dx where 


8 * 

the shearing stress per unit area is s = — r , the differential deflection from 

Yl 


shear is 



8 

L\A 


dx . 



To integrate this we have to express 8 and A as functions of x. The 
cross-section, A, will be assumed as constant, and for a concentrated load 
S is also constant and equal to the supporting force on that side of the 
load. For a uniformly distributed load 8 is equal to the algebraic sum of 
the forces on one side of the plane of shear, which here must be taken 
normal to the deflection. Thus for any section distant x from the end of 

p 

the beam we have for a concentrated load at the centre 8 = —, a con¬ 


stant, while for a beam uniformly loaded (supported 


cases) S = 


P (l 


at the ends in both 


Using these values in eq. (3G), we have for the 

Deflection of a learn from shear when supported at its ends and 
loaded at the centre, 




or at centre A s 


PI 

IE S A' 


• • ( 37 ) 


Deflection of a beam from shear when supported at its ends and 
uniformly loaded , 

dY ° = itJi- x ) dx ’ 


or 


Vs = 


p fix X 


I 77 — 77 ], or at centre A s = 


E % A\ 2 2 


pF 


8 &A 


• • • 


• (38) 


Hence the total deflections at the centre for these two cases are 


A F \i%EI + 4 E 3 a) .( 39 ) 

and 

A _J 5? 4 t F \ 

~ ? \ 38477 ” r 8E,A/’ .( 40 ) 

* Assuming also that the shearing stress is uniformly distributed over the cross- 
section. 















MATERIALS UNDER CROSS-BENDING STRESS. 


C7 


for beams supported at the ends and loaded with a single concentrated load 
P at the centre, and with a uniformly distributed load of p per unit of 
length, respectively. 

For the metals take E s — \E, while for wood take E, = \E. The 
fibrous character of wood may explain the apparent anomaly. 

For solid rectangular wooden beams, therefore, we have 

1 r 2 i * 7> 2 

For load at centre , from (39), making E s = \E, and —= —= — _ 

A I 12 1 


A = 


PI 


48 El 


iP 4" 5A 2 ),.(41) 


and 


For beam uniformly loaded, from (40), 


'=&(!+*•) . <«> 


These equations show that when a rectangular wooden beam loaded at 
the centre has a length less than seven times the height, the deflection 
from shear is more than ten per cent of the total deflection, while for such 
a beam uniformly loaded the deflection from shear exceeds ten per cent of 
the total when the length is less than about six times the height. 

47. Determination of Young’s Modulus of Elasticity from Bending 
Tests.—Since E enters in all the expressions for deflection of beams, it is 
evident that it may be found from a bending test where all the dimensions, 
loads, and deflections are observed. Thus for a beam of uniform, solid, 
rectangular cross-section, supported at the ends and loaded at the centre, 
we should have, from eq. (33), for a long beam where deflection from 
shearing forces could be neglected, 

e-NL-AN-IL ( 43 ) 

Since in testing a beam the stress on the extreme fibre is also desired, the 
last form of this equation may be useful in case / is also to be computed. 
However, this value of / must be inside the elastic limit in order to use it 
in computing E. 

It is best to measure a series of coincident loads and deflections, and 
plot them as in Fig. 49, then draw a tangent to the curve at the origin 
and use this in finding E. Thus the tangent line OA is used for comput¬ 
ing E, and the coordinates of any point on this line may be taken . It is 
convenient to take a point representing a deflection of unity. On this 
curve this corresponds to a load of 6250. The dimensions of the beam 
were l = 140 in., b = 4.02 in., h = 8,04 in., and the material was long-leaf 









68 


THE MATERIALS OF CONSTRUCTION. 


yellow pine (Pinus palustris). Using the second form of eq. (43), 
we have 

PC 6250 X 140 3 


F = 


±Abh 3 4 X 1 X 4.02 X 8.04 : 


= 2,070,000 pounds per square inch. 


The maximum load was 13,500 pounds, from which we find, by eq. (6), 
the computed maximum stress on the outer fibre to be 

f — ^ ^ = 10,000 pounds per square inch. 



Fig. 49. 


The elastic-limit load might be taken as 9000 pounds, whence the fibre- 
stress at this limit would be 


3 W'l _ 3 X 9000 X 140 
' “ 2 iW ~ 2 X 4.02 X 8.04 2 


7300 lbs. per square inch. 


48. The Rational Designing of Flitched Beams.*—A hitched beam is one 
composed of two sticks of timber enclosing between them a wrought-iron 
or steel plate of the full length of the sticks, these three members being 
rigidly bolted together, preferably along the neutral plane, in such a way 
that they will act as one solid member when deflecting under a load. In 
order that these two materials may come to their working stresses simul¬ 
taneously, the iron or steel plate should always be of less depth than that 
of the timber. 

To find the relative depths of steel (or wrought iron) plate and the 
timber sides in order that they shall come to their working stresses at the 


* This problem is introduced here, not because it is very common or important in 
itself, but because it is a good type of composite systems and illustrates the method 
of analyzing such systems. 







































































MATERIALS UNDER CROSS-BENDING STRESS. 


69 


same time, we must utilize the principle that when two or more members 
jointly carry a single load , they share this load in direct proportion to their 
relative rigidities. The rigidity of a beam is the inverse of its flexibility, 
and the flexibility is measured by the deflection under a given load. Hence 
the rigidity will be measured by the reciprocal of the deflection. The 
equation representing the deflection of a solid rectangular beam, in terms 
of the stress on the outer fibre, is, from eq. (33), since 


1 PI 

M — — fbh* = — for a load P at the centre, 
o 4 


PI 3 _ fTbh? _ fT 
4 SET ~~ TTeI “ GFh’ 



But since the rigidity is measured by the reciprocal of the deflection, 
we have as a measure of the rigidity of a rectangular beam, in terms of the 
stress on the outer fibre, 

R = 


1 QEh 
rigidity = ^ = 


fC 


.(45) 


We may now write the proportion: 

Deflection of the . deflection of the t > the rigidity of . the rigidity of 
wooden beam * steel plate ' * the plate * the beam, 


or 

A W * ^ s • • Rs * E IV) - R 

But 

R s _ 6E s h s > Q>E w li w _ E Ji s f w 

Ti w ~ ~JJ ^ f J* ~ E w h w f s • 


Hence we have for a flitched beam, in which A w = A s> 




^w__R±_ TTT _ 1 

A s R w BJiJs 


(48) 


where R w = rigidity of the timber sides; 

R s = same for the steel plate; 

A w — deflection of the timber sides; 

A s = same of the steel plate; 

E w = modulus of elasticity of timber = from 1,000,000 in white pine 
to 1,800,000 in long-leaf yellow pine; 

E 8 = modulus of elasticity of wrought iron and steel = 28,000,000; 

P z=z total load on flitched beam; 

P w = load carried by the timber sides; 

P s = same for the steel plate; 

f w = working fibre-stress for timber = from 1000 in white pine to 
1800 in long-leaf yellow pine; 

f s = same for steel = 12,000 to 18,000 pounds per square inch; 














70 


THE MATERIALS OF CONSTRUCTION. 


h w = depth of the timbers in inches; 
h s = same for the steel plate; 
b w = total thickness of both timbers in inches; 
b s = same for the steel plate. 

From eq. (48) we may derive many important relations: 

(a) To find the relative depths of steel plate and wooden beams to give 
simultaneous working stresses in each. Eq. (48) may be written 



h s E w f s 


(49) 


Example: Let E s = 28,000,000, E w = 1,400,000, f s = 16,000, f w = 1600; 
then 

h w 28,000,000 X 1600 _ 0 
J~ s ~ 1,400,000 X 16,000 


That is to say, the wooden sides must be twice as deep as the steel plate, 
regardless of their respective thicknesses, in order to give a working stress 
in the wooden sides of one tenth that in the steel plate. 

(b) To find the relative stresses on the outer fibres when the plate is of 
the full depth of the timber sides. We now put eq. (48) in the form 

fvj E w h w 

'77 ~ ~eJi 7 . 

Using the same values of E as above, and making h w = h s , we have 

fw _ E w _ 1 
fs E s - 20* 

Hence when the steel or iron plate has the full depth of the wooden sides, 
the stress in the outer fibres of the timber is onlv one twentieth that in the 
plate. This does pretty well for a white-pine and steel combination. 

But in the ease of white pine we should not take E w higher than 
1,000,000. Hence we have for white pine and steel of equal depths 

fw E w 1,000,000 1 

fs E s 28,000,000 28’ 

That is, the maximum stress in the timber is only fa that in the steel plate. 
For an elastic limit of steel of 40,000 pounds per square inch we may have 
a working fibre-stress of 20,000 pounds per square inch. This would give a 
fibre-stress of 700 pounds per square inch in the timber sides, which is 
hardly a sufficiently high working stress for white pine. All these conclu¬ 
sions are quite independent of the relative thicknesses of plate and sides. 

To find what part of the total load P is carried by the timber sides and 
by the steel plate respectively, we may let P w and P s represent these loads, 
so that P w -f- P s = P. Also the total load P divides itself between the 
parts in proportion to their respective rigidities, these rigidities being now 











MATERIALS UNDER CROSS-BENDING STRESS 


71 


taken as the reciprocals of the deflections when expressed in terms of the 
equal loads If instead of fibre-stresses. From eq. (44) we have 


A. = b = S and 


whence we have 


Pf 


P„ 


'W 


• w 


PJ 


• . . (51) 


& 


P 


IV 


R 


w 


PJs 
p [ ‘ 

-P-'w-Lio 


hut for solid rectangular sections I = -f^bld j hence we have 

A 


_ Esbsha ... 

~ E r „bjh t 


' lV w W ,t/ W 


-But Py, — P Psj which substituted in (51) and reduced gives 

P 


P s = 


1 + 


EJuAR' 

E s b s h s 3 


Similarly, 


P = 

W - 


1 + 


E s b s h s 


= P — P 

x X S» ••••#* 


P wb w Ji w 


(52) 


(53) 


(54) 


(55) 


Thus if the depths and thicknesses of the plate and of the timber sides bo 
known, the parts of the total load which they will carry can be found from 
equation (54) or (55), or their relative values may be found at once from 
equation (53). 

Example: Dimension aflitched beam 24 feet long to carry a distributed 
load of 2000 lbs. per foot. 

Assume a depth of timber sides of 1G inches, and let the plate be the 
full depth of the timbers. If we use “long-leaf” pine, we may take 
E w — 1,400,000, while E s = 28,000,000 for the steel plate. Eq. (50) now 


f l 

gives us J ~ = —. That is, the maximum fibre-stress in the timber sides is 

fs ~0 

one twentieth that in the steel plate. We will also assume the plate to be 
% inch thick. If it is stressed to 20,000 lbs. per square inch, the load i*t 
alone will carry is found from eq. (G). Thus 



Psl 

8 



or P s = 12,000 lbs., nearly. 


This leaves 36,000 pounds to be carried by the timber sides. 

But when the stress in the plate is 20,000 pounds, that in the timber sides 
is but 1000 pounds. Hence we must now find the combined breadth of the 
two sides to carry 36,000 pounds with this fibre-stress. Here again we have 

M l0 = = M 0 — f wbw h , L j or b w = ^ = 30 inches, nearly. 

o 0 

















72 


THE MATERIALS OF CONSTRUCTION . 


As this thickness is out of the question, we might double the thickness 
of the steel plate, making it 1 inch, when it will carry 24,000 pounds, leaving 
24,000 pounds for the timber sides. This would reduce them to 20 inches 
in width, or two sticks, 10 in. by 1G in. each. 

If it were practical to obtain timbers 18 inches deep, they would serve 
the purpose much better. (The student might redimension the beam on 
this assumption.) 

It is evident from the above that there is no economy in combining iron 
and wood in this manner. An iron or steel I beam or a plate girder should 
always be used in such a case when this is practicable. The problem has 
been inserted here as a valuable exercise. 

49. Steel and Concrete in Combination.—It is now common to employ 
steel wires or bars to strengthen the tension sides of concrete beams. To 
analyze this case it is necessary to know the modulus of elasticity of the 
particular concrete employed, and at the age when its working strength is 
first required. This property of concrete has seldom been observed (see 
Chapter XXX), but for good Portland-cement concrete it may be taken at 
1,000,000. For cinder concrete, such as is used in fire-proof flooring in 
buildings, it is very much less, possibly not over 100,000. 

Referring again to the general proposition that in composite structures the 
load divides itself between the systems in direct proportion to their relative 
rigidities, we conclude that for like areas, similarly placed, the rigidities are 
to each other as their moduli of elasticity. Since the modulus of elasticity 
of steel is 28,000,000 and of the concrete, say, 1,000,000, it follows that one 
square inch in section of steel resists for equal deformations as much as 28 
square inches of concrete similarly placed. To find the resistance of the 
combined material, therefore, substitute an amount of concrete for the steel 

wire or bar equal to twenty-eight times 
its cross-section, adding this in the hori¬ 
zontal plane of the steel bar, and then 
treat this new form of section, as shown 
in Fig. 50, as an actual beam of concrete. 
By finding its moment of inertia, the 
strength of the beam, when the concrete 
fails by cracking on the tension side, may 

fl 

be found from the equation M 0 = ~, 

y i 

where / is the ultimate tensile strength of the concrete ; I is the moment of 
inertia of the transformed section ; y x is the distance from the neutral axis 
of this section to the tension side of the beam; and d/ 0 is the moment of 
resistance of the actual beam when the concrete cracks.* 



Fig. 50.—Steel and Concrete in 
Combination. 


* For a discussion of the case where the concrete cracks and the elastic limit of the 
steel bar is reached, as well as for the case where the concrete cracks on the tension side 
and then fails in compression because of the strength of the steel bar, including also the 
case here treated, see an article by the author in Engr. News , Jan. 3, 1895, p. 10. 



















MATERIALS UNDER CROSS-BENDING STRESS. 


72 a 


lib — breadth of concrete beam, 
h = height “ 


sc 


cc 


a — area of steel bar, 


E a 


A = substituted equivalent area of concrete — a~ f 

Eq 

E s = modulus of elasticity of steel, 

E c = “ “ “ “ the concrete used, 

e = distance from centre of beam to centre of bar, 

d = “ “ “ “ “ “ new neutral axis, 

y l — “ “ neutral axis to tension side of beam, 

= “ “ “ “ “ compression side of beam, 

f t = stress on outer portion of the concrete on the tension side, 
f a — a “ “ “ “ “ « « compression side, 

/ = moment of inertia of the transformed cross-section, 

6 if 

f o = stress on outer portion of beam if no steel bar were used = 
m = — . used for convenience (but is in fact the ratio of the lon- 


a E, 


then we have 

e 


gitudinal rigidity of the beam to that of the steel bar). 


h 


d = trri> y ' = 2~ d ’ 


y. = l + d‘, + 


Tensile stress on concrete at ) _ „ _ My x „ 

f — ft — — Jo 


bottom 


Compressive stress on con¬ 
crete at top 


f -Mi- f 

J c J Jo 



1 m + 12 


If the steel bar be a flat plate and this be placed at the bottom of the 

h 

beam, but buried in the concrete, then e — - and we have 


Tensile stress on concrete at bottom =f/ 
and. similarly 

Compressive stress on concrete at top — fj 



(A') 

(BO 


If the steel rod, or plate, be removed still farther from the body of the 
concrete, by placing it in the lower side of a projecting rib of concrete, then e 

becomes greater than Equations (A) and (B) will still apply to this case, 

merely using the true values of e and h, not counting the projecting rib as 
any part of the concrete beam. Thus if a concrete floor 4 inches thick be 
supported by ribs every two feet, in the bottoms of which are steel rods J. 










7 2b 


TEE MATERIALS OF CONSTRUCTION. 


inch square, so placed as to be 10 inches below the centre of the concrete 
floor, then from equations (A) and (B) we have 

f < == °- oo7 f° and =°- u % 


T.4< 


m m 


where / 0 = = 


bh* 384* 


If any particular ratio of compressive to tensile strength of the concrete 

f 

is to be developed, we may impose the condition^ = k; whence for the steel 

Jt 

placed at the bottom side of the beam we have, from equations (A') and 

<B'), 


fc _ J c _ m + 2 
ft vi 3 


bh E c 

or m = -ft 

a E s 


2 


k - 1’ 


f 

whence, for ^ = k, 
Jt 




a = 


E, 


bh(k — 1 )E 0 


2E S 


(C) 


Thus if = 5, we have, for -==- = —, a = 


f 


E s 28’ 


bh 

14’ 


That is to say, if the steel plate covered the entire base of the beam, it 
■would have to be y 1 ^ as thick as the concrete and steel combined to satisfy 
dhis condition, it being assumed in this and all former cases that the con¬ 
crete does not crack on the tension side. Evidently it is impracticable to 
develop the full compressive strength of the concrete by this construc¬ 
tion, on condition that the concrete is to remain unbroken on the tension 
side. 

To find the total stress in the steel bar, we assume it to stretch the same 
as the parts of the concrete beam adjacent to it; hence for any given position, 
distant e from the centre of the beam, we have 


y E 

Total stress on steel bar = J Xe — d)~X a = 

/, Ec 

If e = ~, this becomes, for the bar at the bottom, 

/V 

Total stress on steel bar at bottom 


2f 0 eb 


1 + w + 12 


V_ 

li 1 


(D) 


/6M\ 


m + 4^ h ) m ’ (iy) 
Eor this case the tensile stress in the steel rod, in pounds per square 
E ... E s 

inch is or it is ~ times as much as that in the concrete adjoining it. 

±J C J-J c 

This stress in the steel bar can never be more than from 2000 to 5000 
pounds per square inch in rock or gravel concrete, but in cinder concrete it 
would be very much more. To utilize the strength of the steel, therefore, 
in rock concrete, it is necessary either to allow the concrete beam to crack 
on the tension side or to remove the steel bars to the lower portions of 
projecting ribs. 













MATERIALS UNDER CROSS-BENDING STRESS. 


72 c 


Ultimate Strength of Combination Steel and Concrete Beams. 

The previous equations apply only so long as both the steel and the 
concrete are acting to resist the bending moment of the external forces. As 
shown, the steel cannot carry much load until after the concrete cracks, but 
this does not open widely at any one point, because of its adhesion to the 
steel bar. It will open in a series of fine cracks, as shown in Fig. 50 a. As 

f 

i 

I 
i 
i 
i 

±. 


these fine cracks would not be a serious matter in most cases, the engineer 
may decide to accept them as a condition preceding the ultimate or break¬ 
ing load, although they should never appear for the greatest working load. 
In this case a new set of formulas is required for computing the ultimate 
load, and the following are offered,* these being based on the following as¬ 
sumptions, the first one being rigidly true and the other two very nearly true: 

1. In simple cross-bending the total compressive stress is equal to the 
total tensile stress acting on any right section of the beam. 

2. A section which is plane before bending remains a plane after bending, 
whence the deformation of any element varies directly as its distance from 
the neutral axis, and hence, within the elastic limit of the steel bar, the 
stress in it and in the unbroken part of the concrete may be said to follow 
this same law. 

3. The tensile stress on the uncracked portion of the concrete below the 
neutral plane is so small and is exerted so close to that plane that it may 
be neglected in this analysis. 

Let a — area of the steel bar ; 

?y a = distance from the neutral plane to the compressed side of the 
beam ; 

e = distance from the neutral plane to the centre of the steel bar ; 
b = breadth of the beam = distance between the steel rods ; 

JE 8 = modulus of elasticity of steel; 

B c — modulus of elasticity of concrete ; 

f s ■= tensile stress per square inch on the steel bar ; 

f c = maximum compressive stress per square inch on the concrete; 

M s — moment of resistance of the beam for any assumed stress, f s , in 
the steel bar, as at the elastic limit. 

M c = moment of resistance of the beam for any assumed compressive 
stress, in the concrete on the upper side. 

* These equations were first derived by Mr. A. L. Johnson, Assoc. M. Am. Soc. C. E. 



NEUTRAL PLAN 

E API 

rER C 

RACKING 

J LJ i i 

t-4-+4 J-tl-l-L-L-U— 



-tt-tUT.-.- 


Fis. 50a. 





































TIIE MATERIALS OF CONSTRUCTION. 


7'2d 


Then we have, from Fig. 50b and assumption 1, 

compressive stress tensile stress = af s ; 


2 


whence = af 8 , or f c = ^-f s .(1) 



TENSILE STRESS IN STEEL BAR 

Fig. 506. 


From assumption 2 we have 

/< = §/’ .. • • » 

From these equations we may find 

,/ 2 ae _ E s ., 

' b E c v ’ 

The moment of resistance is 

M,= f Ayl +f>ae . ( 4 > 

By substituting for fjb its value from (1) we have the moment of resist¬ 
ance in terms of the stress on the steel bar to be 

M. =/ s (^p + ae) .15) 

By substituting in (4) the value of f s a from (1) we have the moment of 
resistance in terms of the compressive stress in the concrete to be 

M c =.f^+^jby, .(C) 


If both of these moments of resistance be computed for any particular 
beam, the smaller result must be taken as the strength of the beam, as this 
indicates the method of failure. The value of f s must not be taken higher 
than the “apparent elastic limit” of the steel used. If the steel rod 

is placed too near the neutral plane, thus making — relatively large, the com- 

pressive stress in the concrete, f c , as shown by equation (3), may become so 
large as to make this the weakest part of the beam. The most efficient 
method of combining steel and concrete is, evidently, to place the reinforc¬ 
ing steel bars at the bottom of projecting ribs, as is now done in some forms 
of fire-proof construction. 
























MATERIALS UNDER CROSS-BENDING STRESS. 


73 


50. Approximate Determination of the Strength of Flat Elates under 
Normal Forces.*—(«) Flat Circular Plate Supported at the Circumference 
and Uniformly Loaded .—Assume a diametral strip 1 in. in width to be loaded 
over its full width at the ends, but the loaded surface to reduce to a zero 
width at the centre, this load to be p lbs. per square inch. The total load 

on the strip will then be pr, and each end support will be —. The bendin°- 

2 ° 

moment at the centre will be 


M =. V — r- P - *r- V -¥ 

0 9 • 9*3* /-» • •••••• 

fC fyj 0 


o 

rJ 


But for a solid rectangular section we have 

M 0 = ifblr , or, for b, 


whence 


= ^ or / 
6 6 ’ 7 


i; 

p^. 
h 


2 ; • • • • • 


h = rj/j., 


where h — thickness of plate in inches; 
r = radius of plate “ “ ; 

f = stress in extreme fibre in pounds per square inch; 
p = pressure on plate in “ “ “ “ 


From a very elaborate analysis, Prof. G rash of finds for this case 



(57) 

(58) 


h — — 0.91 r\Z'y. 

(b) Square Fled Plate Supported at the Periphery and Uniformly Loaded . 
—Since the corners are more distant from the centre and therefore carry a 
less proportion of the load, we may assume that the opposite sides act inde¬ 
pendently, so far as the bending moment at the centre is concerned. On 
this assumption the plate may be regarded as supported at two sides only 
and loaded with one-half the actual load, whence we have 

M. ■■= i fapbl 2 = if bid, .(59) 

or 

¥ 

f 

where l = length of one side of the square plate. 

( c ) Same Cases when the Plates are Fixed in Position at their Periph¬ 
eries .—Since the maximum bending moment on a beam' fixed at the ends 
and uniformly loaded is only J that of a beam supported at the ends and 



n = i\/\i ;= o . ck / 
8 / 


* These proximate solutions are offered as illustrative of simple approximate methods 
which may often be applied to very complicated problems of this class. 









TEE MATERIALS OF CONSTRUCTION. 


similarly loaded, we may assume the same relations would hold here, thus 
giving for a circular plate, rigidly held. 


Spr 2 

7 “ 4 hr 
For a square plate, rigidly held, 

9. P£_ 

J 33 A 1 ’ 


or h = Wj- 


2 


( 61 ) 


or h = 0.53 1 y y. . . 


(62) 


(d) For Elliptical and Rectangular Plates .—Here the plate fails by 
cracking along its greater axis; and since the deflection of a beam for a 
given load is as the cube of the length, it is evident that the ends carry but 
a small part of the total load. Where the longer axis is more than twice the 
shorter one, we may neglect these end bearings entirely when we have the 
case of a flat plate supported at two opposite sides, which then becomes a 
simple beam: and this is the proper assumption to make in such a case. 

Making this assumption, and calling 1) the smaller dimension of the opening,, 
we have 


_ 3 pF 

J A 


4 h* 9 

Prof. Bach gives for this case 

CcdPp 


7 & i/3 P 

or h = ~ 2 V T 


(63) 


/ = 




(64) 


(a s + iyi 1 

where C is somewhere between f and 1. 

When the longer axis is about 1 \ times the shorter , as is common with 
manhole-covers, assume that } of the total load is carried at the sides, thus 
giving, from (64), 


, 3 3 pF . 

/ = 4 ‘ 4 H?’ ° r h 




( 65 ) 









CHAPTER VI. 


THE RESILIENCE OF MATERIALS. 

51. Resilience Defined .—Resilience is literally the springing back of a 
deformed body after the deforming force has been removed. As used in 
mechanics, however, it is the work done by the body in this springing back,, 
which is the same as the work done on the body in deforming it, so long as 
this is inside the elastic limits. Beyond the elastic limit the work of 
deformation always exceeds the work given back by the body. The body- 
then does not fully recover its initial position, shape, or dimensions. 
Sometimes the work of deformation, whether inside or beyond the elastic- 
limit, is spoken of as the resilience, but this is improper. The resilience 
proper is the amount of work, or energy, in foot-pounds, which can be stored' 
in an elastic body, up to a given stress per square inch, and which can be 
given out again by the body as useful work, if desired * That portion of the 
energy spent in deforming the body but not given back as resilient work is 
spent in permanently deforming the body, by causing the particles to move 
or slide over each other, thus developing heat. The elastic deformation 
of a body does not develop heat. Since work is measured by a force 
acting over a distance, the work of deformation may be measured by 
the product of the deforming force into the distance through which it 
acts. But the deforming force is zero at first and increases uniformly as 
the deformation increases (inside the elastic limit); hence the total work 
done in deforming a body is the average value of the force into the total, 
deformation. Since the force increases uniformly with the deformation, its 
average value is always one half its final value (inside the elastic limit), so 
that the work of deformation, or the energy stored in the body , is one half 
the product of the final force (or resistance), into the deformation. Inside 
the elastic limit the stress-diagram (for all kinds of stress) is a straight line,, 
and here also the resilience, or work given back, is equal to the work of 
deformation. Hence the elastic resilience is equal to the triangular area of 
the stress-diagram, included between this curve, the axis of deformation, 
and an ordinate parallel to the axis of loads, to the extremity of the locus 
developed. As similar areas are to each other as the squares of their like 

* This is the sense in which Young first used the term in 1807, but he did not so 
clearly define it since he assumed bodies to be perfectly elastic to rupture. 


75 




76 


THE MATERIALS OF CONSTRUCTION. 


parts, or dimensions, it is evident that the elastic resilience, or energy, 
stored in a body is as the square of the unit stress under the final load, this 
unit stress being equal or proportional to the load ordinate in the stress- 
diagram. It will be shown hereafter that this is true for all kinds of 
resilience, both inside and beyond the elastic limit. 

52. Three Varieties of Resilience— There are three kinds of resilience 
commonly recognized, namely, of tension or compression, of bending, 
and of torsion. These, of course, correspond to the three corresponding 
kinds of stresses and deformations. It will be shown below that the 
elastic resilience of a body, in foot-pounds or inch-pounds , is always equal 
to the product of three factors, namely: 

(a) A numerical coefficient, which is different for each of the three hi nds 
of resilience, and for different forms of cross-section, and for different 

methods of applying the external forces. 

r 2 

(o) The factor ~, or the square of the maximum stress divided by the 

Hj 


modulus of elasticity. 

(c) The volume of the body. 

That is to say, for any particular kind of stress and form of cross- 
section the elastic resilience varies directly as the square of the stress- 
intensity and as the volume of the body, and inversely as its modulus of 
elasticity, or 



. volume 



That is to say, the resilience, or energy, which can be absorbed, or stored , 
in a body of a given material and form, up to a given fibre-stress, is no 
function of the relative dimensions of the body, but only of its volume. 
In other words, one cubic inch of steel will absorb and give out the same 
amount of work, or energy, as the same volume of fine wire, if the load is 
applied in the same manner, or if the stress is of the same kind, so long as 
the form of cross-section remains the same.* 


53. Resilience a Measure of the Ability of a Body to Resist a Shock or 
Blow. —The magnitude or effect of a blow, or of a falling body, is measured 
by the energy stored in the moving body at the instant of impact. In the 
case of a body which has fallen freely in space under the action of gravity, 
its energy is Wh, where W is the weight of the body (force of gravity), and 
h is the distance through which the body has fallen freely (distance through 
which the force of gravity has acted). In any case, the energy of the body 

is ——, where v is the velocity in feet per second, and g is the acceleration 


o 


r J 


* When the stress is direct (tension or compression), the form of cross-section is 
immaterial. In bending and torsion, however, the form of section is important. 





TEE RESILIENCE OF MATERIALS. 


77 


of the force of gravity, or 32 feet per second. If a moving body, as a 
falling weight, is stopped by striking a fixed solid body, which is here 
assumed to be a test specimen, the energy of the moving body is spent in 
one or all of the following ways: 

(a) In deforming the moving body itself, either within or beyond its 
elastic limit. 

(b) In a local deformation of both bodies at the surface of contact, within 
or beyond the elastic limit. 

(t-) In moving the fixed body as a whole, with an accelerated velocity, 
the resistance consisting of the inertia of the body. 

(d) In moving the fixed body against its external supports and resistances. 

(e) Finally, in deforming the fixed body as a whole against the resisting 
stresses developed thereby. 

If the moving body be very hard and rigid; if the surfaces of contact are 
comparatively unyielding; if the specimen have a small mass as compared to 
the moving body, and if it be very rigidly supported upon or against a very 
great mass or weight which is relatively unyielding; and, finally, if the spec¬ 
imen which is to receive and absorb the energy of the blow is quite yield¬ 
ing or flexible, and in short if there is nearly absolute rigidity in all parts of 
the apparatus except in the body struck, and if this yields only as a whole 
and not at the point of contact or at its supports,—then, and only then, 
can nearly all the energy of the moving or falling body be absorbed by the 
deflection or stretch or compression or twisting of the specimen. It is prac¬ 
ticable, by making the energy of the falling body consist mostly of weight 
and only to a small degree of velocity, that is, by having a heavy weight drop 
through a short distance, to absorb up¬ 
wards of 90$ of it iii the specimen. It 
goes without saying that it is impossible 
to get it all stored in the specimen 
under any circumstances; and if great 
care is not exercised in arranging the 
test, but a very small percentage may 
be given over to the specimen, the 
rest being dissipated in the other ways 
named above. 

In the stress-diagram shown in Fig. 

•51 let the vertical ordinate represent 
total resistance in pounds and the hor¬ 
izontal ordinate represent deformation 
of the body, as a whole, measured at the 
point of contact, in inches; whether this 
deformation be a bending, extension, 
compression, or twist is not now material. When this body has been de¬ 
formed to d x it is resisting this action with a force of jtq; when deformed 











78 


THE MATERIALS OF CONSTRUCTION. 


to d 3 it is resisting with a force of p 3 , etc. W hen the deformation passes; 
the elastic limit the resistance does not increase as rapidly as the deformation, 
and hence the diagram is no longer a straight line, but becomes curved. 
A deformation of d 3 now d-evelops a resistance of p 3 , and d t of , etc. 

Now since the work of resistance is the sum of the products of the in¬ 
stantaneous resistances into the corresponding deformations, it is properly 
represented by the area of the stress diagram up to the maximum deforma¬ 
tion and resistance. That is to say, the work done on the body to deflect or 
deform it to d x is indicated by the area of oq x d x \ the work required to de¬ 
form it to d 3 , and also the energy stored in the body when deformed to this 
point, is indicated by the area oq 3 d 3 , etc. So long as the point q falls on the 
stress diagram inside the elastic limit, this amount of energy stored will all 
be given back again by the body. But when this point q falls beyond the elas¬ 
tic limit point of the diagram, the body is no longer able to fully recover its 
original form, but it remains permanently deformed. The amount of this 
permanent set can always be found by dropping lines q 9 q % 'q A q t ', etc., from the 
extremity of the diagram which marks the maximum load imposed, 'parallel 
to the straight portion of the curve. These lines are the return paths which 
the specimen follows on the removal of the deforming forces or loads. They 
are always parallel to the elastic path of the body, or to that part of the 
curve below the elastic limit. This is true for all kinds of stresses and dia¬ 
grams, whether tension, compression, bending, or torsion; and whether the 
vertical ordinate represents total loads or resistances, or loads per square 
inch, or intensities of stress on extreme fibres. 

In case the specimen has had to absorb an amount of energy, or work, 
represented by the area oq 3 d 3 , therefore, it will give back only so much as is 
represented by the area y 3 'y// 3 . The remainder, oq 6 qf represents work 
which has been spent in permanently deforming the specimen, and which it 
can never give back, this having been transformed into heat by friction. 
Under our definition of resilience, therefore, we should have to say that the 
resilience of the specimen, for the resistance p 3 , is q 3 qfl 3 , and not the full 
area oqgl 3 . This latter represents the work done in deforming the specimen, 
but it cannot properly be called resilience. Similarly, when the body is dis¬ 
torted to d t with a developed resistance of y> 4 ; the resilience now is q/qgl^ , 
and oq t q A ' has been lost in the permanent deformation of the specimen, or 
in heat. 

The student will readily perceive that the areas of the triangles whose 
bases are od x , od 3 , q/d 3 , and q’d K , respectively, are to each other as the squares 
of these bases, or as the squares of their altitudes, p x , p 3 , p 3 , and p x , respec¬ 
tively, since they are all similar, their sides being parallel. If their altitudes 
represented stresses per square inch, which they might, then we could say 
the resilience of this specimen varied as the square of the stress developed 
in it, as stated in Art. 52, and as will be further shown analytically, whether 
this maximum stress be inside or beyond the elastic limit. 


THE RESILIENCE OF MATERIALS. 


7 £ 


Thus far in studying Fig. 51 we have spoken of the “work of deforma¬ 
tion ” without stating whether this work was developed bv a load slowly ap¬ 
plied, or by one quickly applied, as 


600 




-200 


by a falling weight. In fact it does 
not matter how this work is done, a 
given number of foot-pounds of en¬ 
ergy producing exactly the same ef¬ 
fect, and developing the same stress 
diagram, provided we assume that 
all the energy of the quickly applied 
load goes into the specimen, to pro¬ 
duce this particular deformation. 

This conclusion is also based on 
another assumption , which is, that the 
relation between the deformation and gpp 
its corresponding resistance devel¬ 
oped in the body is the same for a def¬ 
ormation produced suddenly as for 
one produced by a slower application 
of external force. This equality of 
relationship has never been shown, as 
between static and impact applica¬ 
tions of the load; * but it is probable 
that this relation is very nearly inde¬ 
pendent of time, inside the elastic 


JOO 


0 


1. 

Aa 

M 



1 

^ / 

pa 

Aj/n^n 


V 

~Sh 



% 

<3 




o 

^ 




% 

_ 


WMtm 

voomo 


0 M JO ‘ ,// .20 

Fig. 52.—Showing that a greater impact 
stress is required to produce a given de¬ 
formation. (Fr. Com. Rep., vol. n. p. 
344.) 


limit, and with brittle bodies up to rupture, since it is in this case a molec¬ 
ular resistance to relative deformation, and not a resistance to flow or rel¬ 
ative displacement. In the case of plastic or ductile bodies, however, it has 
been shown that beyond the elastic limit the stress diagrams developed by 
impact and by static loads are very different, the former being in the case 
of soft iron wire some 30$ greater in area. This means that for such mate¬ 
rials the actual energy absorbed by the specimen under impact is some 30$ 
more than it is under a static load. See Fig. 52. 

Assuming now that all the energy of a blow is spent in deforming the 
specimen in the manner represented on the static stress-diagram, we come 
to this very important conclusion: the energy of the blow , in foot pounds, is 
equal to the area of the stress-diagram developed by that blow, properly eval¬ 
uated to the scales of the drawing , when this diagram is drawn to co-ordi¬ 
nates representing deformation and resistance thereto. Thus if a weight 
falls on a body, as a beam, and if we may assume that very little of the 
energy spends itself otherwise than in bending the specimen, if the speci¬ 
men deflects by the amount d ,, for instance, then we assume that the corre¬ 
sponding resistance at the instant of maximum deflection is p ,, and that the 
energy of the blow was somewhat greater than the area oqflp, or by know- 

* See description of Russell’s impact testing-machine, p. 380a, for such a determina- 














80 


TEE MATERIALS OF CONSTRUCTION. 


ing the energy of the falling body ( Wh), and observing the deflection pro¬ 
duced, we could determine the amount of energy absorbed by the specimen 
if we only had a stress-diagram of this specimen under impact, as shown in 
Fig. 52. Few such diagrams have ever been obtained. It has been custom¬ 
ary to use for this purpose static test-diagrams, carried beyond the elastic 
limit, and perhaps to failure. This, of course, destroys the specimen for 
impact tests; but by having two specimens, presumably just alike, a static 
test may be made on one of them, from which a static stress-diagram can be 
drawn, and then the impact test on the other specimen can be interpreted by 
this static diagram. Having done this, we should still fail to find the area 
of stress-diagram developed by a single blow fully equal to the energy of the 
blow, because of the dissipation of a portion of this energy in other ways, 
and also because the impact stress-diagram lies above, or outside of, the 
static diagram. 

It is common to test materials by means of falling weights, and often 
the height of drop is regularly increased until failure occurs. Let us follow 
the course of such a test, referring again to Fig. 51. Thus we will suppose 
all the energy of the blow goes into the specimen (or it would serve as well 
to suppose a certain fixed percentage is absorbed by the specimen), and that 
the first blow deformed the specimen to d x , the second to d 2 , the third to d 9 , 
and the fourth to d x . Now what were the energies of these blows, if all 
went into the specimen each time ? Evidently the energy of the first blow 
was that indicated by the area oqglp, of the second by oqflp, of the third 
by oqgfg, and of the fourth by qfq/qf,. Thus we see that all the first area 
is included in the second, all of both first and second in the third, and a 
large part of the third {q z 'qplf) in the fourth. These areas are therefore 
not mutually exclusive, so that the sum of the energies of all the blows 
{NWli) is not equal to the total area of the stress-diagram developed by 
them, oqgl 4 . Neither is the energy of the last blow equal to this area, and 
in fact there is no relation between the total area of the stress-diao-ram. 
i oqft 4 , and the energy of one or all of the blows given. If we now add to 
this statement the evident fact that we can never know in practice what 
portion of the energy of any blow is spent in deforming the specimen (and 
often we cannot tell what this proportion is within over 50$, and sometimes 
it has been assumed that it all went into the specimen when there could not 
have been more tha nfive per cent of it so spent !), it becomes patent that 
NO ABSOLUTE CONCLUSION WHATEVER CAN BE BASED ON IMPACT TESTS. 
Some relative conclusions may be drawn by subjecting two or more like 
specimens to exactly identical treatment and finding which withstands the 
.greater number of blows. Even then the aqiparent relative strength depends 
largely on ivhat particular magnitude of blow be selected for making tests. 
Also a very small difference (apparently) in the character of the foundation 
on which the specimen rests may make a very great difference in the per¬ 
centage of the total energy which goes into the specimen. Hence such 


THE RESILIENCE OF MATERIALS. 81 

comparative tests should always be made on the same foundation, and all 
the elements of the test exactly duplicated.* 

In order to obtain the absolute characteristics of any material, a com¬ 
plete stress-diagram should be obtained by static tests. The area of such a 
diagram up to its elastic limit indicates the total energy of the single shock 
or blow it could withstand up to that limit, or without taking a permanent, 
set (provided this energy all went into the specimen), and the area of this 
diagram, up to rupture, indicates the total energy of the single blow it 
could absorb without actually breaking. 

It must also be observed that in addition to the impact stress being 
greater for given deformations, beyond the elastic limit with ductile mate¬ 
rials, the total elongation at rupture is also much greater when produced by 
a sudden blow than when produced in a static test, and hence the area of 
the stress diagram thus developed may be very much larger than the static- 
test diagram on the same material. 

For an absolute measure of a given material to withstand a shock or 
blow, therefore, it is necessary to give it a static test in some kind of a test¬ 
ing-machine, whether this test be in tension, or in compression, or in cross¬ 
bending, or in torsion. Then the area of the stress-diagram up to the elastic 
limit, divided by the volume of the specimen under test, is a measure of the 
ability of the material, per unit of volume, to absorb and give out energy y 
or to resist repeated shocks without injury ; and the toted area of the stress- 
diagram is its measure to resist a single blow without rupturef 

It is necessary in this connection to guard the student against several 
misconceptions. 

(a) By a “slow” or “ static” test is meant such a gradual imposition of 
the load as will give to the moving parts an inappreciable velocity, or 
momentum, or vis viva. Evidently any ordinary test in a testing-machino 
fulfils this condition. 

(b) By an impact test, or a shock, or a blow, is meant a genuine striking 
or impact, in which the force of the blow is nearly all due to the speed or 
velocity of the moving body or falling weight, and only slightly due to its. 
static weight alone. 

( c ) Aside from the two methods which alone have been under dis¬ 
cussion in this article, there is another method of loading, called a “ sudden 
imposition of load.” Thus in the case of placing a load on a beam, if 
the load be brought into contact with the beam, but its weight sus¬ 
tained by external means, as by a cord, and then this external support be 

*It is not uncommon to find impact tests described by giving only the weight of 
hammer and height of fall, with no description of the character of the supports. It 
lias also been customary to rest stamp-mills on spring-timbers to lessen the force of the 
blow ! 

f Except that for ductile materials, in which the impact stress-diagram is greater 
than the static stress-diagram, as shown in Fig. 52. 



82 


TEE MATERIALS OF CONSTRUCTION. 


suddenly (instantaneously) removed, as by quickly cutting the cord, then, 
although the load is already touching the beam (and hence there is no real 
impact), yet the beam is at first offering no resistance, as it has as yet 
suffered no deformation. Furthermore, as the beam deflects the resistance 
increases, but does not come to be equal to the load until it has attained its 
normal deflection. In the meantime there has been an unbalanced force of 
gravity acting, of a constantly diminishing amount, equal at first to the 
entire load, but now reduced to zero when the resistance has come to be 
equal to the load, at the normal deflection. But at this instant both the 
load and the beam are in motion, the hitherto unbalanced force having pro¬ 
duced an accelerated velocity, and this velocity of the weight and beam 
gives to them an energy, or vis viva, which must now spend itself in over¬ 
coming an excess of resistance over and above the imposed load, and the 
whole mass will not stop until the deflection (as well as the resistance) has 
come to be equal to twice that corresponding to the static load imposed. 
Hence we say the effect of a suddenly imposed load is to produce twice the 
deflection and stress of the same load statically placed. It must be evident, 
however, that this case has nothing in common with either the ordinary 
static ” tests of Structural materials in testing-machines, or with impact 
tests. It is introduced here to prevent a confusion of mind in these matters 
often found to exist with persons whose conceptions of such problems in 
mechanics are not clear. 

54. Resilience Areas in Stress-diagrams. —It was shown in the previous 

article, in discussing Fig. 51, that the shaded triangular areas represented 
the resilience of the specimen for the several loads imposed. It will now be 
shown that these areas may be represented as one figure with continuously 
added increments. 

Referring again to Fig. 51, if the j)ermanent set, oq 3 , be laid off on^ 3 ^ 3 
from giving oq, on ppq^ from p A giving q/', etc., and drawing a curve 
through these points from jt; 2 ,the elastic-limit stress, the curve so drawn 
may be called the curve of permanent sets. If we now regard the space 
intercepted between this and the stress-diagram, it is evident that the length 
of the horizontal intercept increases directly as its altitude above the hori¬ 
zontal axis, since these intercepts are the bases of the similar triangles on 
the horizontal axis, whose apexes lie in those horizontal lines. This curved 
area oppq"q 4 "... qpiMP is therefore a more general type of a true triangle, 
whose area is simply equal to its upper base (the horizontal intercept which 
equals the'elastic deformation) into one half its altitude (which is the maxi¬ 
mum stress produced, or load imposed). In other words, the following 
triangles are equal, because they have equal altitudes and bases. Since 
they also have equal angles at the vertex, they are, in a more general sense, 
similar triangles: 

1 Triangle oqpl^ — triangle oppqp 
Triangle q/cq,d, = triangle oppq^q % qp\ 


THE RESILIENCE OF MATERIALS. 


83 


Triangle q/qfi, = triangle op 9 q t "qf'q A q t q % o. 
etc. etc. 

Hence by simply constructing both the stress-deformation and the 
stress-set curves, we may indicate directly the resilience or work which the 
specimen will be able to give back after having been stressed to any 
assigned limit.* The value of this resilience is always one half the product 
of the final stress into the difference between the final distortion and the 
permanent set; or, in general , whether inside or beyond the elastic limit , the 
resilience is equal to one half the product of the final load or stress into the 
elastic deformat ion .f 

55. Resilience of Bodies under Direct Stress.—When a body of a uni¬ 
form cross-section and of a definite length is subjected to the action of 
external forces, producing direct tension or compression, the deformation 

produced in the body, from eq. (2), Chapter I, is a — If A = the 

cross-section of the body, then the total external force applied is P — pA. 
The total external work is then 

P« = pA pl = \_f A1 
2 2 ' E 2 W Al . 


But since this is equal to the internal work of resistance, and since 
Ad — volume of the specimen, we have 

\ ri 1 

R d — resilience in direct stress = — . ~ . volume; . . . (3) 

nr per unit of voTtme, 

r * = l& .< 4 > 


Since p and E are given in pounds per square inch, the volume must 
also be in cubic inches. 

If p is made equal to the elastic limit of the material, the corresponding 
value of r d is the primitive elastic resilience in inch-pounds per cubic inch. 
Beyond the elastic limit, the elastic resilience is indicated by the triangles 
I/9/1 e ^ c -> i n Fig. 51, corresponding in each case to the new or 

artificially-raised elastic limits jt? 3 , p 4 , etc. These subsequent elastic resili¬ 
ence values may be called the artificially-raised elastic resilience. 

As defined in the previous article, all resilience is elastic resilience, but 
the term “elastic” is retained here in order to insure that it is not confused 
with the term “ total resilience,” which is sometimes misused and made to 
mean the total area of the stress-diagram, which the author of this work 
will not admit is resilience in any sense. 

56. Resilience in Cross-bending.—The deflections of beams loaded and 
supported in different ways, in terms of the stress on the extreme fibre, are 


* When the stress passes a maximum and both these curves begin to descend, the 
included area here becomes negative. 

f True under the author’s definition of resilience, but not true when this term is 
made to mean the work or energy absorbed instead of the energy given back. 









84 


TEE MATERIALS OF CONSTRUCTION. 


given in column four of the table on pages 62-65. For any case the 

fr 

deflection may be represented by the term h where h is a numerical 

coefficient which varies for the different cases, but the values of which are 
given in that table. Since the resilience of a beam when developed by 
falling weights, or other impact loads, would produce deflections corre¬ 
sponding to concentrated loads, only concentrated-load deflections as given 
in the table need be here considered. Thus, for a beam supported at the 
ends and loaded at the centre, the deflection, in terms of the stress on the 

outer fibre, is A — ^ ^ 


g jgj • But the load which will produce the stress /on 

s/T 

The external work 


8 fi 

the outer fibre is (see column five of table) P = 


111 

done on the beam in deflecting it, which must equal the internal work of 
resistance, or the resilience, if/is inside the elastic limit, is 

« 

PA 2 p ll_ 

/?• 


Kesilience = 


2 


3 E 


(5) 


For a solid rectangular cross-section, I = 
Substituting this in eq. (5), we have 


Resilience of a rectangular beam , ivhether solid or laminated , loaded at the 

( 6 ) 


i p i r 

centre and supported at the ends = — /— .bhl = —~ • volume. 
Lr 18 E 18 E 


If the bending moment had been uniform throughout its length, as is 
the case with a spiral or helical spring when under a bending stress, the 
movement of one end of the spring should be determined, and this multi¬ 
plied by one half the final force applied at this point. But since the 
internal work of resistance is always equal to the external work of deforma¬ 
tion, we may measure up the internal work and call this the resilience. 
The case of a beam (or a spring) under a uniform bending moment is a 
favorable case for this purpose. Thus assume a spiral or helical spring- 
made of a steel bar having a rectangular cross-section whose original 
dimensions were l, b, and h. When coiled into a spring (the dimensions of 

the coil being immaterial for our purpose) 
and a couple producing bending moment 
applied to it, thus developing in the spring 
throughout its entire length a moment of 
resistance which we will suppose is such as 
to give rise to the elastic-limit stress / on 
the outer fibres throughout the entire length 
of the coiled bar, we are to measure up the 
total internal work of resistance, or the 
energy thus stored in the spring. Since the fibre-stress is uniformly vary- 



Fig. 53. 










THE RESILIENCE OF MATERIALS. 


85 


ing across the section of the bar, and is f on the outer fibres on each side* 
it is evident that 


The stress on any fibre = p = ay = f ~ = ~- 
where y = distance of fibre from neutral axis, and 

y x = distance of outer fibre from neutral axis = 

/w 

f — stress per square inch on outer fibre. 

But 

The stretch of any fibre = a = jy, 

where p = stress per square inch; 

l = length of bar of which spring is composed; 

E = modulus of elasticity. 

Therefore 

L 

E ' 1C 


y> 


(?) 


( 8 ) 


The work of resistance of any fibre 


y s 


(9) 


The work of resistance of any zone of fibres bcly in area of cross-section. 


2 f ‘ 2 hi 

distant y from the neutral axis, would be -4- . - . y\hp and 

E 1C 


The total work of resistance = resilience = R = 




A 

2 


2 r hi 
E ’ 1C * y dy 


h 
»+ o 

9 r 2 

y'dy = %.. 

h Eh 

2 


JtT'bi 
E ' a- 

l f‘ 

= — • -jj. volume of spring 


bl Cif 


+A 
^ 2 


u ic i p . 

= • — • — = — *4- 6/A 

E 1C 12 6 i? 


( 10 ) 


Comparing this with eq. (5) we see that fifty per cent more energy can 
be absorbed by a beam or spring when subjected to a uniform bending 
moment than when the moment increases uniformly from the ends to the 
centre, or from one end to the other, 

57. Resilience in Torsion. —Referring to Fig. 23 we see that the external 

work is , where 6 is the distortion angle and a = length of arm of the 

/V 

couple, whose forces are P. But from eq. (2), Chapter IV, when the 
moment Pa is on the specimen the stress on the outer fibre is 


j. 2 Pa 
= or 


f 7tr 3 
La- 2 


2 Pal 5 Pal . 

6 — — r -, T = —-p> since E s = \E. 
nr E 8 nr E 5 


Also, from eq. (4), 














86 


THE MATERIALS OF CONSTRUCTION. 


Substituting here the value of Pa above, we have 

6 _ bf s 7tpl _ f ff, 

2nPE 2 rE 

Combining this with the value of Pa again to get the value of 


we 


have 


Pa 6 5 f 2 

Work of torsion on solid cylinder — —— = - . nr 2 l 


5 f 2 

— volume.( 11 ) 

o E 


58. Comparative Resilience of Bodies under Different Kind of Stress.— 

For bodies of uniform cross-section we have the following table of values of 
resilience in incli-pounds per cubic inch , and their relative capacities to ab¬ 
sorb and give out energy, taking the capacity in direct stress as unity. 

COMPARATIVE RESILIENCE OF BODIES. 




Figure. 




1 


m/m/, 



i i 

fj 1 i"’ i’i'1!!!!! |! I!! iT'i 

I V ' 1 1 1111111111111/1 

LUjJJlUJJIUlUJ 




Kinds of Stress. 

Resilience in inch- 
pounds per cubic 
inch. = r. 

Direct tension or compression. 

1 r 

2 ' E 

Cross-bending with bending 

i r 

moment uniformly increas- 

18 ‘ E 

ing longitudinally. 


Cross-bending with bending 

i r 

moment uniform longitudi- 

6 * E 

nally. 


Torsion. 

5 /* 

8 * E 


Relative Capacity 
for Absorbing and 
Giving out Energy. 


1 


i 

9 


1 

3 


5 

4 

















































EXAMPLES ON PART I. 


86a 


EXAMPLES ON PART I. 

• 1. A section of a steel bar 1 in. in diameter and 8 in. long elongates 0.01 in. for 
an increase in tensile stress of 80,000 lbs. What is the modulus of elasticity ? 

. 2- What reduction in temperature would bring a wrought-iron bar, immovably 
fixed at its ends, to its elastic limit of 26,000 lbs. tensile stress per square inch? 
Take E = 28,000,000 and the coefficient of expansion = 0.0000065 per degree F. 

Am. 142°.8 

3. Find the proportionate change in volume of a brass cube which is subjected to 
a compressive stress in one direction of 10,000 lbs. per square inch. Take E — 
15,000,000. What is its change in volume for a fluid pressure of this amount in all 
directions? Ans. 0.00023; 0.00069. 

■4. What is the shearing modulus of elasticity for steel if .£' = 29,000,000 and 
Poisson’s ratio = 0.27 ? " • Ans. E s = 0.39 E. 

•5. Find the modulus of elasticity of steel from Fig. 6, making allowance for the 
locus cutting the vertical axis at 1000 pounds above the origin. Use the deformation 
of 0.001 and its corresponding stress-increment in pounds per square inch. From 
the same diagram find the elastic limit, the ultimate strength, and the percentage 
of elongation. 

^ 6. The following is a record of a test on cast iron : 

Loads per square inch 

in pounds. 1000 5000 10000 15000 20000 25000 30000 31040 

Proportionate deforma¬ 
tions. 0 .00022 .00055 .00097 .00150 .00220 .00368 broke 

Plot this record and determine from it: (1) The modulus of elasticity; (2) The ap¬ 
parent elastic limit; (3) The total percentage of elongation (by extending the plotted 
curve till the breaking load is reached); (4) The work required to break the speci¬ 
men in foot-pounds per cubic inch of metal (obtained by finding the area of the 
diagram and evaluating it to the scales of the drawing, see Art. 53). 

,7. Assume a brick to be 8 in. long, 4 in. wide, and 2 in. thick. From equation 
(12), p. 31, find the relative crushing strength of the brick per unit area when 
tested flatwise, edgewise, and endwise, taking the strength of a cubical specimen of 
the same material as unity. Ans. 1.22; 0.89; and 0.83. 

8. A stone cube two inches on a side has its edges chamfered or rounded so that 
the bearing surfaces are but 1.8 in. square. What is its total crushing strength as 
compared to the strength of a full cube ? What is its strength per square inch of 
bearing-surface as compared to the strength per square inch of a full cube? (See 
Fig. 18.) Ans . 85 per cent; 103 per cent. 

• 9. By how much is a centrally loaded column 12 in. square weakened by adding 
four inches of the same material to one side of the column without shifting the load ? 

Ans. The maximum stress in the column is increased by 31£ per cent. 

• 10. A steel rod 1/4 in. in diameter and 30 in. long is used as a torsional spring for 
closing a door. What will be the increase in the moment of torsion from giving 
the rod an additional twist through 90°, the shearing modulus of elasticity being 
taken as 12,000,000 ? What will be the maximum increased shearing stress in the 
rod due to this angular movement ? What will be the increase in the force required 
to hold the door in this position, the door-knob being 30 inches from the hinges? 

Ans. 244 inch-pounds; 78,500 lbs. per square inch ; 8 pounds. 

. 11. A wooden beam 8 in. by 16 in. in cross-section and 20 ft. long carries a 
uniform load of 1000 lbs. per running foot. Find the maximum direct stress on the 
outer fibres and the maximum shearing stress in the beam. 

. s 1760 lbs. per square inch direct stress; 

x 11S ‘ \ 117 “ “• “ “ shearing “ 

• 12. For the same beam and load as in Ex. 11, find the deflection of the beam, 

taking E = 1,200,000. If the deflection were observed to be 3/4 in., what would be 
the modulus of elasticity? Ans. 1.1 in deflection; 1,760,000 modulus. 

13. A flitched beam is composed of two sticks 4 in. by 16 in. by 16 ft. long, and 
a steel plate 3/4 in. by 16 in. of the same length, and carries a load of 2000 pounds 




866 


TEE MATERIALS OF CONSTRUCTION. 


per running foot. Find the portion of the load carried by each part, the maximum 
fibre-stresses resulting, and the deflection at the centre, taking E = 30,000,000 for 
the steel and 1.500,000 for the timber 

. ) Steel: 1305 lbs. per foot; 15,660 lbs. ; 0.25 inch. 

Ans - ( Timber: 695 “ “ “ 782 “ “ “ 

14. How many foot-pounds of energy per pound of steel can be stored in a steel 
helical or spiral spring coiled about an axle, by winding it up until the stress ill 
the outer fibre is 80,000 lbs. per square inch, E being taken equal to 30,000,000 ? 

Ans. 17.8. 

15. How much would such a spring weigh which could absorb the energy of a 
street-car weighing 20,000 lbs., and moving at the rate of six miles per hour on a 
down grade just sufficient to overcome the frictional resistances ? Would the size of 
the cross-section of such a spring affect its necessary weight ? 

Could such a spring be designed so as to reach this fibre-stress when the car had 
stopped, and also so as to be exerting the maximum torsional moment on the car- 
axle without causing the wheels to slip ? Is such a device practicable?* 

Ans. 2315 lbs. 

16. To what extent can energy be stored in metallic springs of any sort ? Could 
they ever be used for the storing of motive power ? (This has often been attempted.) 

17. A pendulum, mounted on knife-edges, weighs 50 lbs., and its centre of gravity 

is 8 feet from the pivot-supports. It is moved to an angle of 30° from the vertical, 
and is allowed to swing and strike the centre of a cast-iron bar 1 in. square, resting 
on absolutely rigid supports (or assumed to be such) 2 feet apart. The pendulum in 
falling breaks the bar and moves a horizontal distance of 24 in. beyond its true ver¬ 
tical position before it comes to a stop. What is the shock-resisting capacity of the 
iron in inch-pounds per cubic inch of metal in cross-breaking under a concentrated 
load? Ans. 20.4. 

18. Assuming the stress-diagram of a static test of such a bar in cross-bending to 
be a triangle, what would its final deflection be if the breaking load were such as to 
correspond to a modulus of rupture of 40,000 lbs. per square inch ? 

Ans. 0.88 inch. 


* This is a favorite device with “ car-starter” inventors. See an article by the Author in Jour. Assc, 
Eng. Socs., vol, iv. p. 293. 



PART II. 


MANUFACTURE AND GENERAL PROPERTIES OF THE 

MATERIALS OF CONSTRUCTION. 


CHAPTER VII. 

CAST IRON. 

GENERAL CLASSIFICATION OF IRON AND STEEL. 

59. Importance of the Subject.— While the use of iron in a small way, 
for offensive and defensive weapons of war and for utensils, is doubtless 
older than authentic history,* it is only since its manufacture has become 
possible on a grand scale, by the aid of steam-power, that it has become a. 
common material of engineering and architectural construction. It has 
now nearly replaced the use of timber in engineering works, and it is rapidly 
replacing the use of wood, stone, and brick in architectural designing. So 
dependent now are all kinds of construction on the use of iron, that the 
condition of the iron-manufacturing industry is universally regarded as a 
true index of the general state of trade and commerce the world over. Since 
iron, therefore, in its various states, is more used in engineering construc¬ 
tion than all other kinds of materials combined, a corresponding amount of 
space is given to a study of it in this work.f 

* There is now in the British Museum ( a) a sickle-blade found by Belzoni under the 
base of a sphinx near Thebes; ( b ) a blade found by Col. Yyse embedded in the mortar of 
one of the Pyramids ; ( c ) a portion of a cross-cut saw exhumed by Layard at Nimroud. 
These may be of meteoric origin. The reason more specimens of iron and steel are not 
found may be due, however, to their rapid oxidation when exposed to air and moisture. 
The stone and bronze implements have resisted this action, and hence many have assumed 
that in the “ stone ” and “ bronze ” ages no iron was in use. 

f A chronological review of the greatest discoveries and inventions in iron manufac¬ 
ture is here given : 

4000 b.c. to ) Wrought iron by the direct process from the ore in small quantities 
about 1500 a.d. 1 by means of charcoal, and this made into cement- or blister-steel. 
About 1500 a. d.—C ast iron made in Germany with charcoal. 

1620-1735. Cast-iron made by Dud Dudley in England with coke, but the prac- 

87 




88 


THE MATERIALS OF CONSTRUCTION. 


60. Classifications of Iron and Steel. —Iron and steel may be classified 
according to its qualities, structure, and composition, or according to its 
methods of manufacture. Apparently the former is the more significant 
basis of classification, but in English- and French-speaking countries the 
latter basis has come to be universally adopted. We will, however, here first 
classify these products according to their more significant qualities (the 
method used in Germany). 

Iron and Steel classified according to Qualities. 

Malleable. 

Cast, when molten, into a malleable mass or ingot. 

Ingot Iron —cannot be hardened by sudden cooling. 

Ingot Steel —can be hardened by sudden cooling. 

Aggregated from pasty particles without subsequent fusion, 
(puddling process). 

tice lapsed till revived in 1735 by Abraham Darby. Blast from leather 
bellows driven by water-power. 

Cement-steel melted in crucibles by Huntsman near Sheffield, England. 
The steam engine oiWatt applied to produce the blast for making pig 
iron, and to drive rolls and hammers in working the wrought iron 
and steel. 

Grooved rolls of various forms, driven by the steam-engine, aud 
wrought iron made from pig iron by “dry-puddling,” both by 
Cort, England. White iron used in the “dry” process. These 
inventions lie at the base of the supremacy of Great Britain in the 
iron trades. 

Hot blast , used in blast-furnaces in Scotland by Neilson, thus greatly 
cheapening the cost of production. 

The “wet-puddling ” process of making wrouglit-iron, or “pig-boil¬ 
ing,” introduced by J. Hall, England. 

Use of manganese in making crucible cast steel, introduced at Sheffield 
by J. M. Heath, which reduced the cost of steel by 50 per cent. 

The Bessemer process of making steel, patented by Sir Henry Bessemer 
in England (son of a French refugee, born 1813), this “ being of far 
more importance to the world than all the gold of California and 
Australia.” 

Invention of the regenerative gas furnace by Sir IF Siemens in Eng¬ 
land (born in Hanover, 1823), and educated at the Magdeburg Poly- 
technicum and at Gottingen). 

Application of the Siemens furnace to the open-hearth process of mak¬ 
ing steel by P. and E. Martin in France, thus originating the Sie¬ 
mens-Martin process of steel-making now employed for nearly all the 
soft aud mild steel used in structural work, and for steel castings. 
The invention of the basic process of making steel, by which the phos¬ 
phorus of the ore is eliminated, by & G. Thomas and P. C. Gilchrist 
(cousins) in England. (First public demonstration April 4, 1879.) 
By this process the range of ores which can be used for steel-making 
is euormously increased, especially in Europe, while it is used often 
in America. 


1740. 

1760. 

1783-4. 

1829. 

1830. 
1840. 
1856. 

1861. 

1863. 

1878. 



CAST IRON. 


89 


Weld Iron —cannot be hardened by sudden cooling. 

Weld Steel —can be hardened by sudden cooling. 
Semi-malleable. 

Steel Castings —malleable metal cast into final forms. 

Malleable Cast Iron —non-malleable metal (cast iron) cast into 
final forms and then brought to a semi-malleable condition. 

Non-malleable. 

Cast Iron. 

Hard Cast Steel. 

The significant criterion here employed to distinguish between iron and 
steel consists in the hardening effects of sudden cooling from a bright-red 
heat. This is not a very satisfactory criterion, however, since all such 
metal is hardened somewhat by snddeu cooling. 

What are commonly known as steel and wrought iron, however, are 
made by radically different processes—one being the formation of the 
product in a melted, or liquid, state and then casting it into a mould, 
forming what is called an ingot; the other consisting in forming the 
product in a pasty or spongy state in a bath of melted or liquid foreign 
matter, from which it is lifted and immediately forged or rolled. When 
formed in the melted state it is purified from all foreign matter except 
such as enters into its own composition, while when formed in the pasty 
or spongy state, in a bath of melted foreign matter, a considerable 
proportion of this foreign matter or slag is, of necessity, lifted out with 
the pasty aggregation, called a “ puddle-ball," and some of this slag 
remains distributed through the iron even after it is rolled, thus giving 
it a kind of fibre or grain. While, therefore, the mechanical qualities of 
the puddled product may be almost identical with those of the cast product, 
there is always a sufficient difference in their structure, resulting from the 
radical differences in their methods of manufacture, to clearly distinguish 
them by simply examining the fracture, and to warrant a classification on 
this basis also: and this is the customary basis of classification in this, 
country.* We have, therefore, 

Iron and Steel classified according to Method of Manufac- 

TURE. 

Malleable. 

1 Wrought Iron —rolled or forged from a puddle-ball; it contains 
slag and other impurities, and cannot be hardened by sudden 
cooling. 

Steel —rolled or forged from a cast ingot and free from slag and 
similar matter. 


* It has also been recommended by a sub committee of the recent French Commis¬ 
sion. 





90 


TEE MATERIALS OF CONSTRUCTION. 


Soft Steel —will weld (with care), and cannot be hardened by 
sudden cooling (Ingot Iron). Same uses as Wrought Iron. 

Medium Steel —will weld imperfectly except by electricity), and 
will not harden by sudden cooling. Used in Structural Work. 

Hard Steel —will not weld, and will harden by sudden cooling. 
Tool-steel, Spring-steel, etc. 

Semi-malleable. 

Steel Castings —Malleable metal cast into final forms. 

Malleable Cast Iron —non-malleable metal cast into final forms 
and then brought to a semi-malleable condition. 

Non-malleable. 

Cast Iron. 

Hard Cast Steel. 

Neither of these classifications must be construed too rigidly, but they 
fairly define the common usage, so far as the employment of these materials 
in engineering design is concerned. 

THE PHYSICAL PROPERTIES OF CAST IRON. 

61. General View. —While cast iron has been known and commonly em¬ 
ployed since the Middle Ages, it has not been critically and scientifically 
studied till within a very few years. In the last quarter of a century, the 
attention of metallurgists engaged in iron-manufacturing industries has 
been almost wholly confined to the manufacture of steel. The great advances 
which have been made in this direction have caused cast iron to be very 
largely replaced by steel in structural designing, and in other directions, 
and since 1885 steel has also been cast in final forms, the same as cast iron, 
«o that the use of cast iron has been very much diminished, relatively to the 
total iron and steel output. For many purposes, however, cast iron will 
probably never be replaced by any other material, especially since great 
improvements have been made in this direction, as a result of scientific 
•study and experiments devoted in recent years to the manufacture of cast 
iron. 

Much of the matter here given on this subject has been quoted directly 
from the Metallurgy of Iron by Thomas Turner, Associate of the Royal 
School of Mines, England. This work was published in 1895 and contains 
the latest results of scientific research on the subject there treated.* 

62. General Properties. —“ Cast iron consists of metallic iron, together 
with at least 1.5 per cent of carbon. It also contains silicon, sulphur, phos¬ 
phorus, manganese, and other elements in greater or less proportion, but 
these may be regarded as impurities, though their presence is often useful 
or even necessary for the purposes for which cast iron is applied. The pro- 

* When not otherwise credited the quoted paragraphs are from this work. (Clias. 
Griffin & Co., London, and Lippincott, Philadelphia.) 




CAST IRON. 


91 


portion of elements other than iron is usually about 7 per cent of the total 
weight, though this varies considerably and is sometimes very much more. 
Cast iron is fusible at a temperature of about 1200° C. (2200° F.); when cold 
it is hard and brittle, some varieties being much more so than others; 
it is not malleable or ductile, like wrought iron or mild steel, nor can it be 
hardened and tempered like ordinary carbon steel. The iron-founder distin¬ 
guishes between pig iron, or the form in which the metal is obtained from 
the blast-furnace, and cast iron, or the form it assumes after it has been 
again melted; but no such difference is recognized by the chemist, and pig 
iron is merely a variety of cast iron which is produced in a particular form.” 

63. Carbon in Cast Iron. —“ Cast iron, when fused, consists of a saturated, 
-or nearly saturated, solution of carbon in iron. The amount of carbon 
which molten iron can thus dissolve is about 34 per cent of its own weight, 
though the solubility is largely influenced by the presence of other elements. 
With much chromium the maximum solubility of about 12 per cent of car¬ 
bon is reached; with much manganese up to 7 per cent of carbon may be 
dissolved; while with about 20 per cent of silicon the minimum solubility 
■of carbon is obtained, and only about 1 per cent of carbon then dissolves. 
Apart from special alloys, such as those mentioned, it is very unusual to 
meet with less than 2 per cent or more than 4.5 per cent of carbon in cast 
iron. 

“ So long as iron containing some 3 per cent of carbon remains in the 
fluid condition the composition is uniform throughout, and the carbon has 
no tendency to separate from the metal, except with very gray iron; in this 
case a layer of graphite, which often occurs in beautiful plates and is known 
•as kish, may be formed. But when the molten cast iron is cooled to a tem¬ 
perature at which it begins to solidify, it may either retain the carbon and 
solidify in a relatively homogeneous form, called white iron; or it may, in 
solidifying, precipitate the greater part of the carbon in the form of small 
scales of graphite, which, being entangled by, and uniformly distributed 
through, the iron, impart to it a somewhat spongy nature, and produce the 
dark color and soft character met with in gray iron. When about half of 
the carbon is precipitated as graphite, and the rest retained in combination, 
the result is the production of dark gray portions in a matrix of white, and 
the iron is then said to be mottled. 

“ The condition which the carbon assumes on the solidification of the 
mass is dependent partly on the rate of cooling, and still more on the 
nature and quantity of the associated elements. In connection with the 
influence of cooling, cast iron obeys the laws which govern other solu¬ 
tions, for it is well known that slow cooling assists the production of 
crystals, and leads to the formation of crystals of larger size, while witli 
rapid cooling both solvent and the substance dissolved may solidify together. 
In a similar manner slow cooling tends to produce graphitic carbon, and 
the slower the cooling the larger are the flakes of graphite which sepa- 


92 


TEE MATERIALS OF CONSTRUCTION. 


rate. Some kinds of white iron may thus be rendered gray by slow cool¬ 
ing, while some kinds of gray iron may be made perfectly white by rapid 
cooling or ‘chilling/ It is, however, only with intermediate irons that 
the rate of cooling produces a marked effect, for irons which are either 
very white or very gray cannot be changed in this manner. The influence 
exerted on the condition of the carbon by the other elements present in 
cast iron is of the greatest importance; thus manganese and chromium, 
which increase the solubility of carbon in iron, lead to a greater percentage 
of total carbon in the fluid metal, and when the iron solidifies this carbon is 
retained in solution, so that irons rich in manganese and chromium are white 
and no amount of slow cooling will alter this character. On the other hand, 
silicon and aluminum diminish the solubility of carbon in iron; if much of 
either of these elements be present in the fluid metal, it is capable of dis¬ 
solving less carbon, and retains it with less energy when it solidifies; as a* 
result the carbon is precipitated as graphite, and gray iron is produced. 
Just as irons which contain much manganese or chromium are j^ermanently 
white, so metal rich in silicon or aluminum is permanently gray. 

“ The proportion of total carbon in iron to be employed for a given pur¬ 
pose is often of secondary importance; it is governed by furnace conditions, 
and by the proportion of other elements. A moderate alteration in total car¬ 
bon, or in the graphite, will frequently have little effect on the physical 
properties of the product, while a small change in the combined carbon 
will profoundly alter the strength and hardness of the casting. Probably 
no other constituent in cast iron is of importance equal to that of combined 
carbon , and the influence of the other elements is largely due to the effect they 
produce in increasing or diminishing the combined carbon. The following 
percentages of combined carbon will usually be found suitable for the pur¬ 
poses specified: 

* Combined Carbon in 
parts of one per cent. 


Extra soft siliceous gray iron. 0.08 

Soft cast iron. 0.15 

Maximum tensile strength. 0.47 

Maximum transverse strength. 0.70 

Maximum crushing strength.over 1.00 


These figures are, however subject to some variation according to the 
size of the casting and the proportion of other elements. The hardness of 
the metal increases regularly with the increase of combined carbon.” 

64. Silicon in Cast Iron. —“All cast iron contains silicon, in quantities 

* Chemical ingredients of iron and steel are always given in hundredths of one per 
cent. Thus “ twenty carbon ” and “ eight phosphorus ” signifies 0.20 and 0.08 of one per 
cent of each, respectively. Even the common workmen use these terms, though they 
may not always understand them. The word point is often added, as “twenty-point 
carbon.”—J. B. J. 










CAST IRON. 


9:3 


■varying in ordinary cases from under 0.5 to over 4 per cent, while ‘silicon 
pig * is made in the blast-furnace with from 10 to 18 per cent of silicon 
No factor is of greater importance in determining the suitability of a sample 
of cast iron for any purpose in the foundry than its content of silicou, as 
this element is so constantly present, and its proportion is so variable, while 
the influence it exerts on the condition of the carbon present, and conse¬ 
quently on the hardness and fluidity of the metal, is so marked. It was 
formerly very generally held that silicon was injurious in all proportions, 
and the less there was present in iron for foundry purposes the better. It 
is true that Sefstrom had observed, long ago, ‘ that the carbon in gray iron 
in which much silicon exists, say from 2 per cent to 3 per cent, is wholly, 
01 neaily so, in the graphitic stated * A similar observation was made by 
Snelus in 1870, and was still more plainly stated by Ledebur in 1879. It 
was also known in the United States that certain irons from Ohio which 
were rich in silicon could be used as ‘softeners' in foundry practice, and 
certain Scotch irons were in favor for similar purposes, though the reason 
of this was not understood. It may, however, be claimed that no general ap¬ 
plication of these facts, or accurate knowledge of the principles underlying 
them, existed before the researches of the author, on the ‘ Influence of Sil¬ 
icon on the Properties of Cast Iron,' published in 1885. f Fol* the purpose 
of these experiments cast iron as free as possible from silicon was specially 
prepared by heating wrought iron with charcoal to a high temperature in 
closed crucibles. This was then remelted with a silicon pig containing 
about 10 percent of silicon in proportions necessary to yield any desired 
composition. The trials were made with sufficient material to allow of 
proper mechanical tests being performed, and a graduated series of mixtures 
was prepared. The tension, compression, and ductility tests were performed 
by Professor A. B. W. Kennedy with the testing-machine at University Col¬ 
lege, London, while the hardness determinations were performed by the 
author with a weighted diamond point (see Chapter XVIII) as described 
in his paper on the ‘ Hardness of Metals.' J The chemical analyses were 
checked by J. P. Walton, at that time chemist to the Glasgow Iron Com¬ 
pany, Wish aw." 

“The original pure cast iron was white, hard, and brittle; on adding 
silicon this became gray, soft, and strong; but with a large excess of silicon 
it once more became weak and hard. The results of the mechanical and 
chemical tests are shown graphically in Fig. 55, and it will be observed that 
the proportions of silicon corresponding to the various properties were as 
follows: 


* Percy, p. 131. 

f Journ. Cliem. Soc., 1885, pp. 577, 902. 
% Birm. Phil. Soc., Dec. 1886. 




94 


THE MATERIALS OF CONSTRUCTION. 


Maximum hardness. 

“ crushing strength. 

“ modulus of elasticity. 

“ combined crushing and tensile strength; 

verse strength. 

“ tensile strength. 

“ softness and working qualities,. 

Lowest combined carbon. 


under 0.80 per cent, 

.about 0.80 “ 

, “ 1.00 

trail s- 

. about 1.40 “ 

“ 1.80 “ 

“ 2.50 “ 

.under 5.00 “ 



Pig. 55. —Showing the Influence of Silicon on the Strength and Hardness of Cast Iron. 

(From Turner’s Iron.) 

“ It must be borne in mind that these values are only true for the author’s 
experiments. Experience has since proved that these are approximately cor¬ 
rect in other cases, and that the order is as above given; but in practice the 
size of the castiug and the proportion of other elements will have an impor¬ 
tant influence.”* 

The influence of silicon on the shrinkage of cast iron, in various sizes up 
to 4 inches square, is well shown in Fig. 56. These results have been well 


* See also Arts. 76 and 79. 


























CAST IRON. 


95 


established by Mr. M. J. Keep of Detroit. His results of transverse tests of 
strength and deflection, for varying proportions of silicon, are given in Figs. 
57 and 58, the former being a deduction from the latter. 



Fig. 56. —Showing the Influence of Silicon on the Shrinkage of Cast-iron Specimens 

of Various Areas of Cross-section. (Keep.) 

“ A small addition of silicon eliminates blowholes and produces sound 
castings. As soon as the metal is sound, with the least graphite, the great¬ 
est crushing strength is obtained; this condition also gives the maximum 
density. Further addition of silicon leads to the formation of graphite, di¬ 
minishes the brittleness, and gives the greatest transverse and tensile 
strength. When the graphite increases beyond this point, the metal is di¬ 
vided by the interspersed graphitic material, and the strength and hardness 
decrease. The deflection also increases with the increase of graphite, but 
when the maximum separation of graphite has taken place any further addi¬ 
tion of silicon causes stiffness or brittleness, and so diminishes the deflection. 
White iron shrinks during solidifying more than gray iron, while highly 

































96 


TEE MATERIALS OF CONSTRUCTION. 


siliceous iron shrinks still more than white. Hence on adding silicon to 
white iron the shrinkage is diminished, but an excess of silicon, on the other 
hand, leads to increased shrinkage. Shrinkage appears to closely follow the 
hardness of cast iron, hard irons almost invariably shrinking most; and as 



✓ 


Fig. 57.—Showing Variation in Cross-breaking Modulus of Rupture of Cast iron for 
Different Sizes of Bars and for Varying Percentages of Silicon. (Keep.) 


both hardness and shrinkage depend upon the proportion of combined car¬ 
bon, they" may be regulated by a suitable addition of silicon.”* 

It has been shown by Mr. Keep that the influence of aluminum on 
cast iron is practically the same as that of silicon, equivalent effects 
being produced, however, with much smaller proportions of aluminum, 
as little as 0.1 per cent of aluminum causing the iron to become soft 
and graphitic. Since the same effect can be obtained by the use of silicon, 


* Trans. Amer. Inst. Min. Eng., 1888. 

















































CAST IRON. 


97 


which is much cheaper, and since the action of the silicon is more uniform, 
because of the difficulty of controlling the effects of such small proportions 
of aluminum, the use of aluminum for this purpose is not likely to come 
into general use. 


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Fig. 58.—Showing the Variation in Transverse Strength of Cast Iron in Various Sizes 
of Cross-section, up to 4 in. square, due to a Variation in Percentage of Silicon. 
(Keep, Tr. Am. Soc. Aleck. Engrs., vol. xvi., 1895.) 

65. Sulphur in Cast Iron. —“ The presence of sulphur in cast iron tends 
to cause the carbon to assume the combined form, and thus to produce hard, 
weak, and brittle metal. Such iron is also unsuitable for puddling and for 
steel-making, so that hitherto sulphur has been regarded as a specially 
objectionable element. Foundry iron of good quality should not contain 
more than 0.15 per cent of sulphur.” 

66. Phosphorus in Cast Iron. —“ The phosphorus which is present in 
cast iron exists in the form of phosphide, and is in great part eliminated 
with the excess of hydrogen as phosphoretted hydrogen, when the metal is 
treated with dilute sulphuric or hydrochloric acid. For many purposes, 
such as the manufacture of steel by either of the acid processes, or the pro¬ 
duction of wrought iron for conversion into tool steel, it is of prime impor¬ 
tance that the proportion of phosphorus should be as low as possible, and the 























98 


THE MATERIALS OF CONSTRUCTION. 


maximum limit for such purposes is 0.06 per cent. It was formerly held 
that foundry iron should also be free from phosphorus, but the author has 
shown that cast irons of special strength always contain a moderate propor¬ 
tion of this element. If a large proportion of phosphorus be present, such 
as from 2 to 5 per cent, the metal is very fluid when melted, and takes an 
excellent impression of the mould.. On this account such iron is sometimes 
employed for the production of very fine thin castings, but it cannot be used 
for any purpose where strength is required, as the presence of so much 
phosphorus induces great brittleness. The brittleness caused by phos¬ 
phorus is so marked that a practical man can often approximately tell the 
percentage of phosphorus by the readiness with which the pig iron fractures 
when dropped on the pig-breaker. On the other hand, gray pig iron con¬ 
taining merely a trace of phosphorus, such as that from the best hematite or 
magnetite ores, is so soft and malleable as to be somewhat wanting in 
strength and soundness, and hence gives inferior results for rolls, columns, 
girders, and other purposes for which strength is necessary. In exceptional 
cases it is advantageous to have the phosphorus as low as 0.20 per cent in 
cast iron, but it is doubtful whether there is any advantage in going below 
this limit. For ordinary strong castings of good quality about 0.55 per cent 
of phosphorus gives excellent results. For the general run of foundry 
practice, where fluidity and softness is of more importance than strength, 
from 1 to 1.5 percent of phosphorus may be allowed, but beyond this higher 
limit the further addition of phosphorus causes such brittleness as to lead to 
marked deterioration.” 

67. Manganese in Cast Iron. — 44 The proportion of manganese which is 
met with in iron produced in the blast-furnace ranges from a mere trace to 
upwards of 86 per cent, and, speaking generally, the higher the percentage 
of manganese the more valuable is the product, on account of the use of this 
element by the steel-maker. The physical properties of cast iron are not 
greatly altered so long as the manganese present does not much exceed 1 per 
cent, and larger proportions may be present in siliceous iron without pro¬ 
ducing the appearance in the fracture which is so characteristic of man¬ 
ganese. When about 1.5 per cent of manganese is present the iron is very 
appreciably harder to the tool, and is more suitable for smooth or polished 
surfaces. But when the amount of silicon is relatively small, and th^ 
manganese exceeds 1.5 per cent, a white iron is obtained with a glistening 
fracture showing flat crystalline plates, which, when very marked, leads to 
the application of the name 4 spiegeleisen ’ or mirror iron, and which is too 
hard to be cut by cast-steel tools. Spiegeleisen contains up to 20 per cent 
of manganese, but with higher proportions the grain becomes once again 
uniformly close and granular, and a material is obtained which exhibits a 
characteristic light-gray color, and which is so brittle that it may be readily 
pounded in an iron mortar. To these varieties the term 4 ferro-manganese * 
is applied; while for some purposes an iron rich in both silicon and man¬ 
ganese, containing, for example, 10 per cent of silicon and 20 per cent of 


CAST IRON. 


99 


manganese, is produced, and is known as 4 5 6 silicon-spiegel ’ or 4 silicon ferro¬ 
manganese. ’ 

44 From the examination of the tests conducted at Woolwich in 1858,* * * § 
and numerous analyses of selected samples of cast iron of special strength, 
the author concluded that the presence of some manganese was rather bene¬ 
ficial than otherwise in foundry practice, though probably any benefit ceases 
wdien the proportion of manganese is much greater than 1 per cent.f The 
good effect of manganese appears to be twofold; by its own action it leads 
directly to a measure of hardness and closeness of grain which is beneficial, 
while indirectly it is useful in preventing the absorption of sulphur during 
remelting. 

44 The effect of manganese when alone is always to harden cast iron, and 
yet cases have come under the author’s notice in which in actual practice 
ferro-manganese has been added in small quantity to molten metal in a 
foundry ladle, with the result that the iron has been very much softened and 
improved. The reason for this doubtless lies in the fact that manganese 
counteracts the effect of sulphur and silicon, tending to eliminate the former 
and neutralize the latter, and so, where common iron is employed, it some¬ 
times happens that ferro-manganese may be used as a softener. The hard¬ 
ness, however, generally returns if the iron be remelted, as the manganese is 
oxidized and more sulphur absorbed. 

44 Manganese has in this way been employed as a softener. A remark¬ 
able effect is produced on the properties of hard cast iron by adding to the 
molten metal, a moment before pouring it into the mould, a small quantity 
of powdered ferro-manganese, say 1 lb. of the latter to 600 lbs. of cast iron. 
As a result of several hundred carefully conducted experiments the trans¬ 
verse strength was increased 30 per cent, the shrinkage and depth of chill 
decreased about 25 per cent, while the combined carbon was diminished by 
about one half4 These observations accord with those made by the author, 
though in all probability their success depends, as above explained, on the 
peculiar composition of the cast iron used.” 

68. Grading of Pig Iron. — 44 For commercial purposes pig iron is classi¬ 
fied or 4 graded ’ according to the appearance of the fractured surface, the 
first member of the series being taken as the most open-grained gray iron, 
while white iron is taken at the other extremity. 

44 In the southern parts of the United States the following method of 
grading pig iron into nine numbers was adopted in 1889:§ 


1. No. 1 Foundry. 

2. No. 2 Foundry. 

3. No. 3 Foundry. 


4. No. 1 Soft. 

5. No. 2 Soft. 

6. Silver-gray. 


7. Gray Forge. 

8. Mottled. 

9. White. 


* Report, Cast-Iron Experiments , 1858. 

f Inst. Journ., 1886 vol. i. p. 185, 

\ Jour. Franklin Inst , Feb 1888. 

§ Iron Age, vol. xlu. p. 498. 









100 


TEE MATERIALS OF CONSTRUCTION . 


“ The following analyses, published by Cf. L. Luetscher, of the pig iron 
made from the ore of Red Mountain, Alabama, will serve to illustrate the 
composition of the different grades of Southern iron: * 



Silver 

Gray. 

No 2 
Soft. 

No. 1 
Soft. 

No. 1 
Foun¬ 
dry. 

No. 2 
Foun¬ 
dry. 

No. 3 
Foun¬ 
dry. 

Gray 

Forge. 

Mot¬ 

tled. 

White. 

Graphitic carbon. 

3.13 

3.48 

3.53 

3.49 

3.55 

3.48 

3.00 

2.11 

.10 

Combined carbon. 

.02 

.03 

.03 

.07 

.07 

.10 

.57 

1.22 

2.92 

Silicon. 

5.5 

3.5 

3.75 

3.15 

2.40 

2.20 

1.50 

1.35 

.95 

Sulphur. 

trace 

.004 

.005 

.005 

.024 

.025 

.06 

.125 

.30 

Phosphorus . 

.68 

.68 

.68 

.68 

.68 

.64 

.64 

.64 

.64 

Manganese. 

.25 

.26 

.27 

.25 

.22 

.21 

.19 

.14 

.10 


44 It will be observed that the silicon regularly decreases, with one slight 
exception, from 5.5 per cent with silver gray, to 0.95 per cent with white 
iron. At the same time the sulphur and combined carbon increase together 
from mere traces in silver-gray iron to 0.3 per cent of sulphur, and nearly 3 
per cent of combined carbon in white iron. The phosphorus is slightly 
lower with the closer grades. These differences are exactly such as are 
noticed with similar grades in the United Kingdom, the most noticeable 
difference being the remarkably small quantities of sulphur met with in the 
open-grade American iron. That American foundry irons have an unusually 
low percentage of sulphur is a fact which is supported by the results of 
numerous analysts, and which has not yet been satisfactorily explained.” 

FOUNDRY PRACTICE. 

69. “ The Cupola is in by far the most general use for remelting iron. A 
cupola is a small blast-furnace, of which there are many varieties employed; 
they are generally circular in section, and are driven with low-pressure 
blast at or near the atmospheric temperature. The fuel used is generally 
hard coke, though occasionally gaseous fuel or charcoal is employed. 
Usually the melted metal collects at the bottom of the cupola, and is tapped 
off at intervals; in some cases separate receivers are adopted. 

“ When coke is used the fuel consumption varies from about 1^ to 21 
'cwts. per ton of iron melted, being greater with small outputs on account of 
the loss due to heating the cupola with each charge. A small quantity of 
limestone is usually added, as it fluxes off the silica added in the form of 
sand adhering to the pigs, or produced by the partial oxidation of the silicon 
in the iron; it combines with the ash of the coke, and also diminishes the 
amount of sulphur which is absorbed from the coke by the iron. 

“ The blast, which is not heated, is driven by means of a fan, or more 
usually by a blower, the pressure being only a few ounces per square inch. 
In the ordinary form of cupola the blast is introduced through one or more 
tuyeres in a single row around the zone of fusion. In Ireland’s cupola, 


* Inst. Journ., 1891, vol. ii. p. 245. 


































CAST IRON. 


101 


'which was introduced about 1860, two rows of tuyeres are employed, and the 
cupola is provided with boshes like a blast-furnace. The object of the 
upper row of tuyeres is to insure more complete combustion of the carbonic 
oxide, which otherwise passes through the charge unburned.” 

70. Influence of liemelting. —“ It is observed that when cast iron is 
remelted it becomes harder and more close in texture; if the metal operated 
be soft, the casting is stronger than the original iron; but when hard iron is 
used, it becomes still harder, and weak, like ordinary foundry scrap. There 
has long been an impression that remelting improves cast iron, but that this 
is not so is proved by melting the metal in a carefully covered crucible, 
where no change in composition takes place, and the properties of the iron 
are unaltered. In some experiments by Sir W. Fairbairn,* a sample of 
No. 3 Eglinton gray iron was remelted in an air-furnace 18 times, test-bars 
being cast at each melting, and it was found that the iron improved up to 
the twelfth melting, and afterwards rapidly deteriorated. Other experi¬ 
ments were performed shortly afterwards, in connection with the manufac¬ 
ture of cast-iron ordnance, in which marked improvement was noticed on 
remelting cast iron, and keeping it for a longer or shorter period in a state 
of fusion. No explanation of these effects was given, but the experiments 
were referred to in numerous text-books, and led to the belief that remelting 
per se was beneficial, though it was observed that the number of remeltings 
recpiired to produce the best effect varied largely with different samples. 

“ By the kindness of Professor Unwin, who assisted in Sir W. Fairbairn’s 
•experiments, the author was supplied, more than thirty years after the tests 
were made, with samples of the test-bars, and was enabled by their analysis 
to clear up some of the difficulties which had surrounded the subject, f 
The results of the author’s analyses were as follows: 


No. of Melting. 

Total Carbon. 

Combined. 

Silicon. 

Sulphur. 

Manganese. 

Phosphorus. 

1 

2.67 

0.25 

4.22 

0.03 

1.75 

0.47 

8 

2.97 

0.08 

3.21 

0.05 

0.58 

0.53 

12 

2.94 

0.85 

2.52 

0.11 

0.33 

0.55 

14 

2.98 

1.31 

2.18 

0.13 

0.23 

0.56 

15 

2.87 

1.75 

1.95 

0.16 

0.17 

0.58 

16 

2.88 

• • • • 

1.88 

0.20 

0.12 

0.61 

18 

• • • • 

2.20 

.... 

• • • • 

• • • • 

• • • • 


“ It will be noticed that, owing to the oxidizing effect of remelting, the 
proportion of silicon steadily diminished, while sulphur was at the same 
time absorbed from the furnace gases. The natural effect due to these 
changes was produced upon the condition of the carbon, which, instead of 
being almost wholly graphitic, became nearly all combined, thus producing 
8 , hard, white iron, which was deficient in tenacity, and brittle. The 

WSki r> ■ i ■ ■■ ■ . . ... . ' 

* B. A. Report, 1853, p. 87. 
f Journ. Chon. Soc., vol. xltv. 1886, p. 493. 



















102 


THE MATERIALS OF CONSTRUCTION. 


elimination of manganese with the silicon, the increase in the percentage of 
phosphorus due to its concentration in a smaller quantity of metal, and the 
initial increase of total carbon for a similar reason, are all in accordance with 
what is observed whenever iron is melted in the air, and when the resulting 
slag is not strongly basic. 

“ The physical effects produced when cast iron is remelted are thus 
merely indications of chemical changes which have taken place in the 
material, while the nature of these changes, and hence the effect produced 
by remelting, will vary with the composition of the iron employed and the 
oxidation to which it is subjected. 

s ‘ In Sir W. Fairbairn’s experiments the metal was melted in an air- 
furnace, but in ordinary practice a cupola is employed. Here the oxidation 
is greater, while as the iron melts in contact with the fuel it more readily 
absorbs sulphur. As a consequence, though the changes which take place 
are of the same kind, and follow the same order as that previously given, 
the effect of each melting is more marked. This is illustrated by the follow¬ 
ing analyses,* from experiments conducted by Jiingst in the Imperial 
Foundry at Gleiwdtz: 


• 

1st Melting. 

2d Melting. 

3d Melting. 

Carbon, graphitic. 

2.73 

2.54 

2.08 

Carbon, combined. 

.66 

.80 

1.28 

Silicon. 

2.42 

1.88 

1.16 

Suiphur. 

.04 

.10 

.20 

Phosphorus . 

.31 

.30 

.28 

Manganese. 

1.09 

.44 

.36 


71. Moulds. —“ The size, shape, and character of the moulds employed 
in an iron foundry depend upon the class of work in hand; they may be 
conveniently divided into the following four classes: 

1. Green-sand; 

2. Dry-sand; 

3. Loam; 

4. Chills. 

1. “ Green-sand moulds are made of moulding-sand, which is first 
uniformly damped, so as to make it adherent, and is lightly rammed around 
a pattern to obtain the required shape. For common castings, especially 
when of large size, open sand is often used; but for the majority of purposes 
the sand is contained in boxes, which in the United Kingdom are usually of 
cast iron, though wooden moulding-boxes are generally used in the United 
States. Usually there are two boxes, upper and lower, the pattern or 
patterns being placed partly in each box, and the ‘ gate ’ or opening for the 
entry of the metal being commonly in connection with the middle of the 


* lust. Journ., 1885, vol, ii. p. 645. 





















CAST IRON. 


ioe 


castings. Where a hole or passage is required in the casting, a ‘ core ’ is 
employed; this generally consists of sand, moulded into the necessary shape, 
and supported by iron wire or other suitable means. The patterns are 
generally of wood, and if of intricate forms, are made in parts designed to 
allow of their removal from the mould; the several parts are kept in position 
by suitable pins. Green-sand moulding is the process most generally 
adopted, as it is rapid and cheap; it involves the use of no expensive plant, 
and is specially suitable for the production of a large number of articles of 
similar form. Machine moulding is employed by manufacturers who have 
a considerable demand for one class of work, and in such cases sand-mould¬ 
ing machines are coming steadily into favor, though they can never replace 
hand work in a general foundry. 

2. “ Dry-sand moulds are made of a loamy sand which, after being 
roughly moulded into shape, is dried by heat, and then carefully finished 
with the tool. The mould is sufficiently soft to be readily cut, though rigid 
enough to retain its shape when the molten metal is poured into it. Such 
moulds have the advantage of giving sounder castings, as they evolve less 
gas, while where a single casting is needed they save money, as no pattern is 
required. When, however, a pattern has once been prepared, green-sand 
moulds are much cheaper. 

3. “ Loam-moidds are more particularly employed for curved or spiral 
surfaces of large size, such as sugar-pans, ‘ copper ’ boilers, soda-pans, water- 
pipes, etc. The outer part of the mould is either built up of brickwork, 
held in place with iron ties; or where a number of similar articles is 
required, an iron casing is employed. The inner surface of the mould is 
made of loam, which is laid on by the trowel, and worked by the hand, and 
usually faced with some carbonaceous blacking. The whole is then carefully 
dried before use, one of the most general methods being by the introduction 
of a flame of gas into the interior. Such moulds can, of course, only be 
employed for one casting, and the labor and cost of loam-moulding is much 
greater than that of green-sand. 

4. “ Chills are used when it is desired to produce a casting the outside 
of which is unusually hard. The iron used is generally a close-grained 
gray, and this is converted into white iron where it comes in contact with 
the cold side of the mould during solidification.* A familiar example of the 
use of chills is met with in the prod action of chilled rolls and car-wheels. 
Eolls are cast on end, with a good head of metal, so as to give soundness, 
while as the shanks of the roll are required to be turned to size, these are 
cast in sand, and are, therefore, relatively soft. The intermediate part of 
the mould, in which the barrel of the roll is cast, is made up of a number of 
large annular rings of cast iron resting one upon another. These are not 
used cold, or a violent explosion would take place when the hot metal came 
in contact with the cold, and therefore probably slightly damp, chilling 
surface. The mould is, on this account, heated to a temperature of about 
150° to 200° C. before the metal is introduced, and the iron is caused to enter 

* See Plate III. For article on Chilled Car-wheel Metal see Journ. Frank. Inst.. 
Apr. 1897, from which the figures in PI. Ill have been taken. 







104 


THE MATERIALS OF CONSTRUCTION. 


from the bottom, and in an oblique direction. By this means a circular 
motion is imparted to the metal, and thus, as it rises, it collects all dirt 
and impurities on its surface, and so fills every crevice of the mould.’’ 

72. Moulding-sand.—“ The proper selection and preparation of mould¬ 
ing-sand has an important influence on the appearance and quality of the 
castings produced in the foundry. The mould must be capable of retaining 
the fluid metal in every direction, but at the same time it must allow of the 
free passage of the air which is collected, and the gases which are generated 
when the mould is filled with hot iron. It must give to the casting a. 
smooth, clean surface, and hence must neither act upon, nor be affected by,, 
the fluid metal at the high temperature at which they are brought in con¬ 
tact; the higher the temperature is that is necessary to retain the metal in 
the perfectly fluid condition, the greater is the difficulty of complying with 
this condition. Thus moulds for cast iron require more careful preparation 
than those for brass, while those to be employed for steel castings require 
still more careful attention. Moulding-sands consist chiefly of silica, 
together with variable proportions of alumina, magnesia, lime, and other 
metallic oxides; coal-dust is also frequently added in small quantity. The 
higher the proportion of silica the more refractory the sand becomes; but 
it is then apt to be wanting in cohesion, and to be difficult to mould, while 
the moulds crack in drying, or are injured by the flow of metal. Alumina 
and magnesia impart cohesion and plasticity, though excess, especially of 
alumina, causes it to be less refractory. Magnesia is refractory, forming a 
good cement for siliceous sand, but when present in quantity it renders the 
mould less porous. Lime and other metallic oxides render sand less refrac¬ 
tory, and should be avoided as far as possible. If the lime be present as 
carbonate, gas will be given off at high temperatures, and will produce rough 
surfaces in the casting; while if it be present as silicate, it will cause the 
sand to adhere to the surface of the hot metal. According to Kohn,* a 
suitable composition for green-sand moulding is approximately as follows: 
Silica, 92 per cent; alumina, 6 per cent; oxide of iron, 1.5 per cent; and 
lime 0.5 per cent; while sand for stove-dried moulds is usually richer in 
alumina and oxide of iron. According to the same author, a composition 
largely used in steel-works for moulding purposes is prepared from Sheffield 
ganister, which is mixed with sufficient magnesia and alumina to give a 
product containing about 85 parts of silica, 5 to 10 of alumina, and 5 to 10 
of magnesia. 

In addition to the sand being of the right chemical composition, which 
condition affects its plasticity and refractory nature as above indicated, it is 
also necessary that it should be of proper degree of fineness, as when the 
particles are too coarse the surface of the castings is inferior, and the sand is 
wanting in cohesion, while when the sand is unusually fine it is unsuitable 
for large castings, as the gases cannot so readily escape.” 


* Iron Manufacture , p. 55. 






Plate III 



Fig. 1. Sand-mould, Not Chilled. 


Fig. 2. Chilled on One Stde. 



Fig. 3. Chilled on Four Sides. 



Fig. 4. Chilled on Opposite Sides. 



Fig. 5. Soft Iron, Chilled on 
Opposite Sides. 


Fig. 6. Hard Ikon, Chilled on 
Four Sides. 


All llie figures iu this plate represent car-wheel iron, except Fig. 5. 

Apr. 1897. 


Journ. Frank. Inst. 



9 















































CAST IRON. 


105 


73. Effect of Size and Shape.—“ The strength and solidity of a casting are 
affected by the bulk of metal employed, and by the form of casting made. 
Thus if a sample of pig iron which would be suitable for a casting of small 
size be employed for making very heavy work, it will be found that owing- 
to the slower cooling in the latter case the grain of the metal becomes much, 
more open, and the strength is proportionally diminished; on the other- 
hand, if the same metal were used for very small castings, the chilling in the- 
mould would tend to make the product close and hard, and in many cases 
this would be so marked as to make the castings quite brittle. The grade of 
the iron used must therefore depend upon the size of the casting to be made, 
the general rule being that a closer-grained or less siliceous iron must be used 
for large than for small castings. At the same time it is generally found 
that the strength of a large casting per unit of area is somewhat less than 
that of a smaller one, since the closeness of grain is usually, though not 
always, associated with increased tenacity. 

“It is also very important that in large castings, where strength is 
required, no sharp or re-entering angles should occur, as these in all cases 
lead to the formation of planes of weakness in the casting. When the metal 
cools in the mould a crystalline structure is developed, the crystals forming 
at right angles to the cooling surface. If this cooling surface be curved, the 
crystals interlace so as to yield a strong casting of uniform structure, while, 
on the other hand, whenever a sharp angle of curvature takes place a plane 
of weakness is the result.” 

Cast-iron columns, used in architectural construction, are commonly cast 
in a horizontal position, thus offering a very poor means of escape for 
loosened sand, cinder, etc., which foreign matter often collects on the ujyper 
side and greatly weakens the column. Furthermore, these are often 
covered by a thin coating of iron. Such faults, found in many columns 
which had been accepted and used * in a public building in St. Louis, are 
shown in Plate III. 

74. Shrinkage of Cast Iron.—“ Although cast iron, especially when very 
gray, expands at the moment of solidification, and thus gives a sharp im¬ 
pression of the mould, the subsequent cooling from a red heat to the ordinary 
temperature leads to a still greater contraction, and the net result is that the 
casting is always smaller than the pattern from which it is made. For this 
reason it is usual in pattern-making to allow about of an inch per foot for 
shrinkage, and if the casting is required 1 foot long, the pattern is made 1 
foot and of an inch in length. The shrinkage in castings is, however, by 
no means a constant quantity, but varies with the relative dimensions of the 
castings and with the character of the metal used; as much as yL of an inch 
per foot being allowed when casting beams, and only ^ with large cylinders. 
Not unfrequently much loss and inconvenience is occasioned in foundry 
work by variations in the shrinkage, caused by altering the shape or propor¬ 
tions of a pattern, or by the use of a different variety of iron. 


* They were removed after the faults were discovered. 





106 


TEE MATERIALS OF CONSTRUCTION. 


“ In the author’s experiments on cast iron it was noticed that silicon pig 
shrank most in the mould, though no accurate determinations of shrinkage 
were made. The subject has since been carefully investigated by W. J. 
Keep, of Detroit, whose experiments embody the whole of the trustworthy 
data available, and who measures shrinkage by casting bars in sand between 
iron chills 12£ inches apart. The contraction is carefully measured by 
means of graduated wedges which are inserted between the ends of the cold 
bar and the iron chill in which the bar was cast. Mr. Keep concludes that 
when silicon varies, and other elements do not vary materially, castings with 
low shrinkage are soft, and that -as shrinkage increases, hardness increases in 
almost, if not exactly, the same proportion. For ordinary foundry practice 
the scale of shrinkage agrees with the scale of hardness, so long as sulphur 
and phosphorus do not vary over wide limits. This is an important fact; 
and as shrinkage tests are very easily performed by an ordinary workman, 
the subject is worthy of more attention than it has hitherto received.” * 

“It is stated that charcoal iron has usually a melting-point which is 
considerably higher than that of less pure iron made with coke. Charcoal 
iron, therefore, sets more quickly in the mould, and contracts more, so that 
an extra allowance for shrinkage must be made in the patterns employed.” f 

THE MECHANICAL PROPERTIES 0E CAST IRON. 

75. “ Hardness of Cast Iron.—The hardness or softness of cast iron is in 
many instances of the greatest importance, as the metal has to be turned, 
planed, tiled, or otherwise worked with tools; hence a number of methods 
have been devised at various times, with the object of determining relative 
hardness. In the older form of apparatus, such as was used by the American 
Ordnance Commissioners in 185(5, an indentation was made in the surface of 
the metal to be tested. By determining either the force required to make 
a hole of a given size, or, on the other hand, the size of the indentation 
produced by a given force, a measure of hardness was sought to be obtained. 
Such a method is, however, erroneous unless the tenacity of all the specimens 
to be examined is the same, as otherwise a deeper hole will be produced in 
the weaker metal, irrespectively of hardness, j; In the author’s researches a 
weighted diamond was employed for determining the hardness of cast iron, 
and the results obtained with increasing proportions of silicon are graphically 
represented in Fig. 55. When very little silicon was present the metal was 
extremely hard owing to the large proportion of combined carbon, while 
when sufficient silicon had been added to convert the greater part of the 
carbon into the graphitic form the maximum softness was obtained. With 
further additions of silicon the metal became harder owing to the hardening 
effect of silicon itself, and for this reason an excess of silicon, beyond about 
3 per cent, is injurious to the working qualities of the metal.” 

* W. J. Keep, Silicon in Cast Iron , p 22. f Kohn, Iron Manufacture . p. 57. 

\ The French Commission recommend this tes., for hardness, using impacts of known 
value in place of static pressure. See Chap. XVIII.—J. B. J. 



CAST IRON. 


107 


76. Hardness and Strength of Cast Iron. —“ When cast iron has to be 
turned or otherwise worked the hardness is of considerable importance, 
while in some cases smoothness of surface and general perfection of the cast¬ 
ing are of the utmost moment. Hard cast iron is brittle, deficient alike in 
crushing, transverse, and tensile strength, and seldom gives smooth clean 
castings. With metal which is a little less hard the maximum crushing 
strength is obtained; while on rendering it a little softer, or, as the workman 
would call it, ‘ moderately hard,’ the maximum transverse strength is 
observed. \\ ith slightly softer cast iron the highest tensile tests are 
obtained, while still softer metal works with the utmost facility, though it is 
deficient in strength. It will be seen, therefore, that when the general 
connection between hardness and strength has been fully grasped, the iron- 
founder requires only the information how to harden or soften his metal at 
will, by the use of silicon or other agents, to be able to produce castings in 
which crushing, transverse, or tensile strength shall predominate as desired, 
or in which softness and fine surfaces shall be the most characteristic feature. 

“ There is a somewhat prevalent idea among founders that if considerable 
strength is required a hard iron must be employed. Doubtless this is to some 
extent true in connection with crushing and transverse tests, but is certainly 
not correct with tensile strength. In all specimens of exceptionally high 
tensile strength examined by the author the metal was a soft good working 
iron, specially suited for engineers’ purposes. In the accompanying table 
is a summary of the author’s results on the tenacity and hardness of cast 
iron, as affected by alterations in the proportion of silicon.* The working 
qualities of the specimens are also given, and it will be seen that the hard¬ 
ness as determined by the sclerometer agrees very closely with the observa¬ 
tions of the workman. It will be noticed, however, that hardness and 
tensile strength do not vary together, but on the contrary high tensile 
strength is met with in the softer irons.” 


TABLE I.—INFLUENCE OF SILICON ON THE HARDNESS AND TENACITY 

OF CAST IRON. 


No. 

Silicon 
per cent. 

Tensile 
Strength 
in Lbs. per 
Sq. In. 

Hardness 

by 

Sclerom¬ 

eter. 

Working Qualities, as determined by the Workman. 

1 

0.19 

22,700 

72 

Very bard indeed. 

2 

0.45 

27,600 

52 

Very bard, tbougb not so bard as No. 1. 

3 

0.96 

28,500 

42 

Hard, tbougb softer than No. 2. 

4 

' 1.96 

35,200 

22 

Good, sound, ordinary, soft-cutting iron, of ex¬ 
cellent quality. 

5 

2.51 

32,800 

22 

Ratber harder than No. 4. 

6 

2.96 

27,400 

22 

Like No. 4. 

7 

3.92 

25,300 

27 

Like No. 6, but rather harder. 

8 

4.75 

22,700 

32 

Ratber harder than No. 7, tbougb not unusually 
bard. 

9 

7.37 

12,000 

42 

Still harder, cutting very like No. 10. 

10 

9.80 

10,600 

57 

Hard cutting iron, tbougb still softer than No. 1. 


* Journ. Chern. Soc., 1885. 





















108 


THE MATERIALS OF CONSTRUCTION. 


77. Crushing Strength. —“ Cast iron possesses an exceptionally high 
crushing strength, and for the majority of purposes the founder relies upon 
this, and does not perform special tests. Usually the tensile strength is not 
above one sixth of the crushing strength; hence if power to resist a tensile 
force is assured, the crushing strength is usually sufficient for ordinary work 
In performing compressive tests it is necessary to have perfectly parallel sur¬ 
faces, and to bed the specimen as true as possible, otherwise the results will 
be low.” 

As shown in Articles 19 and 22, the height of a crushing-test specimen 
of such a material as cast iron should be not less than about twice its 
least lateral dimension. Test specimens of cast iron are usually cylinders 
which have been turned up in the lathe, and hence the length of such a 
specimen should be not less than twice the diameter. The following table 
of values contains the results of a great many tests of cast iron in compression 
on short cylinders, the dimensions being usually one inch in diameter and 
from two and one-half to three inches high. 


TABLE II.—CRUSHING STRENGTH OF CAST IRON. 


Experimenters. 

Pounds per Square Inch. 

Authorities. 

Max. 

Min. 

Mean. 

Hodgkinson. 

Hodgkinson (1849).... 

Woolwich (1858). 

Fairbairn. 

146,000 

121,000 

140,000 

215.000 

207,000 

82,000 

55,000 

44,500 

92,000 

77,000 

107,000 

86,000 

91,000 

Fairbairn, Iron, 1869, p. 218. 
Pole, Iron Construction, p. 84. 
Report , 1858, p. 2. 

B. A. Report , 1853, p. 87. 

J. Chem. Soc., 1885, p. 907. 

Turner. 

. 




While the crushing strength of cast iron in short test-blocks varies from 
50,000 to 200,000 lbs. per square inch, it must never be assumed that any 
such strength can be found in large sizes, as in cast-iron columns for build¬ 
ing construction. Here, from numerous tests made at the U. S. Arsenal 
at Watertown, Mass., and from tests made at Phoenixville, Pa., in Dec. 1897 
(see p. 474), we may not assume an average ultimate strength per square 
inch of over about 34,000 lbs. There are various causes for this reduced 
strength. Since such forms are cast horizontally, with a more or less flexible 
core, which deflects upward under the buoyant action of the melted metal, 
the shell is thinner on one side than on the other. Any defect, also, 
at any point, reduces the strength at this section, and the strength of 
the column is only the strength of its weakest part. Maximum crushing 
strength requires about 0.75 per cent silicon and 2 per cent combined 
carbon. 

78. Transverse Strength. —“As before stated, the maximum transverse 
strength is obtained with metal a little softer than that which possesses the 
highest crushing strength. Transverse strength depends, at least in part,. 





















CAST IRON. 


109 


on the power to resist both a crushing and a tensile force; hence transverse, 
strength is intermediate between crushing and tensile so far as the charactei 
of the iron is concerned. This combination of properties imparts to the 
metal characters which are most valuable in certain cases. For transverse 
tests many shapes and sizes of test-bar have been adopted, and, for scientific 


purposes, the results so obtained are converted by calculation into breaking- 
stress on the extreme fibres in pounds per square inch, which is called 
the modulus of rupture. See Art. 33. For a load in the centre of a, 

3 PI 

rectangular bar we have / = — — f , where 

Z oh 


f — modulus of rupture in cross-breaking : 
P — breaking load at centre ; 
l = length of bar in inches ; 
b — breadth of bar in inches ; 
li — height of bar in inches. 


TABLE III.—MODULUS OF RUPTURE OF CAST IRON". 


* 


Modulus of Rup- 




ture in Pounds 


Experimenters. 


per Square Inch. 
3 PI 

7 3 bit* ' 

Authorities. 

Robert Stephenson, 1847... - 

I Max.. 
Min.. 

58,000 

37,000 

Pole, Iron for Construction , p. 88. 


Max.. 

47,500 


Hodgkinsou and Fairbairn. ■< 

Mia 

29,500 

Box, Strength of Materials, p. 186. 

Mean. 

37,000 


Max.. 

42,500 


Woolwich, 1858. s Min .. 

9,700 

Report, p. 2. 

' 

Mean. 

26,700 


Fairbairn, 1853. 


56,000 

B. A. Report , 1853, p. 87. 

Tm-npr 18K5 

Mux 

63,500 

Inst. Journ., 1886, p. 1. 

A . . 


“ It will be noticed that the modulus of rupture varies from the excep¬ 
tionally low value of 9700 lbs. to 63,500 lbs. The average for common iron 
is about 30,000, while 45,000 is required for better-class castings. For 
specially good work some South Staffordshire founders can produce a 
strength of 60,000 with tolerable regularity. In performing transverse tests, 
care should be taken to avoid even the slightest twist on the specimen, and 
the weights used should be added very gradually, otherwise low and irregular 
results are obtained. The size of bar used has also an influence on the 
strength (as shown in Figs. 57 and 58), the smaller sectional areas giving 
much higher values. It should be remembered that the strength of a test- 
bar does not accurately represent the strength to be expected in the casting, 
if the size of the latter, and the circumstances of pouring, do not pretty 
closely agree with those of the test-bar itself. 















110 


THE MATERIALS OF CONSTRUCTION. 


79. Tensile Strength. —“ In many of the less important foundries tensile 
tests are omitted, but in the better works such tests are generally performed, 
and appear to be growing in favor. It was shown by the American Ordnance 
Experiments (1856) that the tenacity of cast iron usually serves as a guide 
to its mechanical value, and practical experience quite confirms this view. 
Tensile test-pieces are of various forms: they are sometimes used with the 
skin on, at others the surface is carefully turned; sometimes small pieces are 
cast separately, while other founders cast the pieces on to the object which 
is being made. At Rosebank Foundry, Edinburgh, the practice is to cast a 
test-piece on to the top and bottom of each important article; these pieces 
are afterwards broken off, and carefully turned down to a suitable size before 
breaking. Such a method is calculated to give a result very nearly approach¬ 
ing what may be expected in the casting itself; for not only is the test-piece 
of the same composition as the casting, but it is also cast under as nearly as 
possible the same conditions as to temperature, pressure of metal, and rate 
of cooling, all of which have a considerable effect on the strength of the 
product. 

“ The following table condensed from a paper by the author will serve 
to illustrate the results obtained by different observers: * 


TABLE IV.—TENSILE STRENGTH OF CAST IRON. 


Experimenters. 

Pounds per Square Inch. 

Authorities 

Max. 

Min. 

Mean. 

Minard and Desnormes, 1815 .... 
Hodgkinsou and Fairbairn, 1837. 

“ “ “ , 1849. 

Woolwich, 1858. 

20.300 
22,000 
23,500 

34.300 
35,200 
40,800 

12,200 

13,400 

9,200 

10,600 

• • • • 

16,000 

16,800 

15.300 

23.300 

Tredgold , 4tk Ed., p. 230. 

B. A. Report, 1837, p. 339. 

Pole, Iron Construction, p. 79. 
Report, 1858, p. 2. 

J. Chem. Soc. , 1885, p. 580. 

Turner, 1885. 

Rosebank, 1886 . 



“ It will be seen that the highest tensile strength of British iron above 
recorded (40,800 lbs.) was obtained in the experiments at Rosebank Foundry 
in 1886. The average tensile strength obtained by earlier experimenters 
was about 16,000 lbs., while in 1858 the mean was raised to 23,000 lbs. 
This increase represents a real improvement in the metal tested, and was due 
to a selection of the more suitable irons as a result of increased knowledge. 
Foundry practice has since improved, and some engineers now stipulate that 
a bar one inch in section shall be capable of bearing a weight of 22,400 lbs. 
for twenty-four hours without fracture, and this apparently severe test has 
been complied with. Contracts are now satisfactorily executed in which a 
minimum strength of 27,000 lbs. per square inch is required, and to produce 
this nothing but Cleveland iron is employed. The author has also succeeded 
in regularly producing an iron of excellent working qualities, with a tensile 


* J. S. C. I, vol. v. p. 289. 


























cast IRON. 


Ill 


strength of 29,000 lbs. per square inch, from a mixture costing under two 
pounds (ten dollars) per ton, and consisting of cast-iron scrap and siliceous 
iron. This is a striking instance of the value of combined chemical and 
mechanical knowledge to the iron-founder. 

“ In foreign cast iron some tensile strengths have been recorded which 
have not yet been equalled in Britain, though probably these results are to 
be regarded as quite exceptional. Thus Professor Ledebur records a tensile 
strength of 42,700 lbs. per square inch with German iron,* while the Ameri¬ 
can Commission on Metal for Cannon, in 1856, obtained a maximum of 
46,000 lbs., and at the Wassiac furnaces, New York, 47,500 lbs. have been, 
obtained.f Much difference of opinion has been expressed as to the value 
of tensile tests for cast iron, as the metal is now never used in tension. 
Professor Ledebur, who is probably the best authority on this subject in 
Germany, states that tensile tests should always be made; and the author’s, 
experience leads to the conclusion that where a complete system of tests, 
such as that of W. J. Keep, cannot be adopted, no other test affords so good 
an indication of the value of the metal, as cast iron with high tensile strength 
is almost invariably soft, sound, and fluid. In the following table seven 
analyses by the author of samples of cast iron of unusually high tensile 
strength are given, together with the results obtained at Woolwich in 1856, 
and at Wassiac. Full details of the preparation of these samples are given 
in the original paper.” \ 


TABLE Y.—COMPOSITION OF CAST IRON HAVING A HIGH TENSILE 

STRENGTH. 



Woolwich 
Experiments, 
1858, Average. 

Silicon Experi¬ 
ments, 1885. 

Rosebank Irons, 1886. 

Dumbarton 

Irons. 

Wassiac Iron. 

Average. 

Tensile Strength 
Pounds per sq. in. 

f-- 

35,000 

40,700 

38,200 

37,200 

36,700 

37,000 

o 

o 

o 

CO 

o 

o 

03 

rH 

37,500 


Per Cent 

Per Cent 

Per Cent 

Per Cent 

Per Cent 

Per Cent 

PerCent 

Per Cent Per Cent 

Per Cent 

Graphitic Carbon 

2.59 

1.62 

• • • • 

• • • • 

• • • 

• • • # 

2.90 

2.60 

2.31 


Combined Carbon 

• • • • 

0.56 

0.36 

0.58 

0.52 

0.40 

0.32 

0.30 

0.78 

6.475 

Silicon . 

1.42 

1.96 

1.29 

1.50 

1.13 

1.33 

1.34 

1.63 

1.31 

1.434 

Phosphorus. 

0.39 

0.28 

0.56 

0.47 

0.41 

0.70 

1.09 

1.10 

0.29 

0.587 

Sulphur. 

0.06 

0.03 

0.06 

0.07 

0.06 

0.05 

0.14 

0.12 

0 08 

0.014 

Manganese. 

0.58 

0.60 

1.00 

1.00 

1.33 

0.65 

1.38 

1.29 

1.51 

1.037 


“ The average composition shown in the above table may be regarded as 
typical for good cast iron when the maximum strength is desired, together 
with soundness and good working qualities. By increasing the silicon the 


* Inst. Journ., 1891, vol. ii. p. 252. 
f Inst. G. E., vol. lxxiv. p. 373. 

\ J. S. C. I, vol. vii. p. 200 










































112 


TEE MATERIALS OF CONSTRUCTION. 


metal becomes more soft and fluid, while by diminishing the silicon the 
transverse and crushing strength, together with the tendency to chill, are 
increased. ’ ’ 

MALLEABLE CAST IRON. 

80. The Product Defined.—White cast iron, or that which has its carbon 
all in the combined form, can be made “ malleable,” or somewhat ductile, 
and nearly doubled in strength, by a process of annealing, by which the carbon 
separates from the iron without forming a mesh or matrix in which the 
remaining iron crystals are imbedded and surrounded, as is the case in 
ordinary gray cast iron. It has hitherto commonly been assumed that this 
change in the iron was effected by means of a decarbonizing agent (oxide of 
manganese, or iron oxide scale), which caused the carbon to leave the iron 
and enter into combination with the surrounding materials, thus making the 
iron malleable. But Mr. II. II. Stanford has shown,* confirming the results 
of Ledebur— 

1. That only about 10 or 20 per cent of the total carbon is lost in the 
process; and, 

2. That the same results are effected when the castings are packed in 
clean river sand—at least so far as the interior portion of the cross-section is 
concerned. It further appears from his investigations that the carbon of 
this interior portion is simply changed from the combined to the graphitic 
£orm (Ledebur’s “ temper-carbon”) at a bright cheny-red, the temperature 
not being high enough to allow the excluded carbon to unite into a more or 
less continuous mesh, but that it is kept in very minute, separated aggre¬ 
gates, thus leaving the decarbonized iron crystals in immediate contact, as 
they are in ingot metal (steel). The advantage of this process lies in getting 
the final forms run from a perfectly fluid iron, at a comparatively low tem¬ 
perature thus obtaining smooth, full, and solid castings, which can then be 
“ decarbonized ” (chemically speaking), without allowing the excluded car¬ 
bon to form in a graphitic matrix. The alternative is to melt and cast 
direct the decarbonized iron (steel), thus making what are known as steel 
castings. This requires a very much higher melting temperature, and thus 
the metal is less fluid, and it is apt to contain gases, or to generate them in 
the mould from the excessively high temperature at which it must be poured. 
The effect is that steel castings are apt to be rough and unsightly on the 
■exterior and more or less porous on the interior. 

When cast iron cools slowly from the melted state the carbon, which is 
wholly in solution or in chemical combination, passes largely into the 
graphitic form (as shown in Fig. 72), this graphite forming a complete 
matrix, and producing the dark, leaden appearance of gray cast iron. In all 
large or thick castings the cooling is of necessity slow (except when pur¬ 
posely chilled at the surface), and hence such forms are not radically changed 

* Trans. Am. Soc. C. E., vol. xxxiv (1895), “Notes on Manufacture and Prop¬ 
erties of Malleable Cast Iron,” by H. R. Stanford, Assoc. M. Am. Soc C. E. 





OAST IRON. 


113 


in their molecular composition by the annealing which constitutes the essen¬ 
tial feature of the malleable process. Only small castings, therefore, are 
suited to this process, unless a very hard white cast iron is used, which does 
not change in cooling to gray iron when cast in thicker or heavier masses. 
It is essential to the successful working of the process that the original cast¬ 
ings shall have the carbon wholly, or nearly so, in the combined form, which 
then changes to an ununited graphitic form when kept some five days at a 
bright cherry-red heat. The only essential characteristics of the packing 
material are, according to Mr. Stanford, such as prevent it from fusing or 
adhering to the castings, or from caking together in hard lumps, and that 
it should not be too expensive. The packing serves only to exclude the air 
and to hold the cast forms to their normal shapes, when heated and softened, 
except as to the decarbonizing action of iron-scale packing on the superficial 
portion of the forms so treated, as described below. 

81. Method of Manufacture.—The original castings, which have hitherto 
been made only of charcoal pig iron, may as well be made from coke pig 
iron,* provided the sulphur be kept low, the essential requirement being 
that the castings shall show all white iron (all carbon in the chemically 
combined form). These are then packed carefully in cast-iron annealing- 
pots, about 18 inches by 24 inches in cross-section, and four feet high, made 
in three sections for convenience of packing, the sections fitting together 
with bell and spigot ends. The castings are so placed in the pots that such 
settlement as occurs in the oven will not deform them. They are surrounded 
by the packing material, which is usually a decarbonizing agent for their 
outside portions, but which serves mainly only as a suitable bedding or pack¬ 
ing for large cross-sections. When large forms are to be treated, they are 
placed and covered in the oven, without the use of annealing-pots. The iron 
pots waste away rapidly by oxidation, being able to serve only about five 
heats, of five days each. 

The annealing-oven may be any suitable oven in which the temperature 
may be kept nearly constant, and uniform over its entire bed. This requires 
that a portion of the combustion shall be completed in the oven itself. 
About five days are required to fully effect the change in the condition of 
the carbon, after which the furnace is allowed to cool down, the first 24 
hours with closed doors. The cost of the treatment is from one-fourth to 
one-half cent a pound 

The effect of sulphur in the cast iron is to greatly delay the change in 
the carbon state, thus largely preventing it, for the ordinary periods of treat¬ 
ment or requiring a greatly extended period of annealing to fully accomplish 
it. Thus iron containing 0.04 per cent sulphur will anneal in three and one- 
half days, while iron in the same sizes containing 0.20 per cent sulphur re¬ 
quires about nine days. Hence if coke iron is used the sulphur ingredient 
must be looked to 


* On the authority of Mr. Stanford. See paper quoted above. 




114 


THE MATERIALS OF CONSTRUCTION. 


Clean, heavy-forge iron-scale seems to be the best material to use for 
packing the castings in the annealing-pots, and these, being composed of 
iron oxide, having a strong affinity for carbon, do extract a large part of the 
carbon from the exterior y 1 ^ inch of the surface of all castings so treated, 
leaving a bright-colored envelope (on the fracture), containing very little 
graphitic carbon. This skin is very much stronger than the interior, as 
shown by Fig. 59, from which it appears that the removal of this portion 
reduces the strength per square inch by 25 per cent. This argues that the 
outer skin is more than twice as strong as the interior* It is necessary to 
establish this fact by further experiment before accepting it as a general 
truth. 

82. Mechanical Properties of Malleable Iron. —From what has been said 

it is evident that “ malleable iron ” is an extremely various product, depend¬ 
ing on the materials used in the cast, and also on the treatment. The 
following table is taken from Mr. Stanford’s paper, which shows what may 
be accomplished by this process. The test specimens were inch in 
diameter, and were tested without dressing down either on the gripped endsf 
or on the reduced portion. The small reduction in total carbon (which all 
occurred in the outer portions) and the change from combined to graphitic 
carbon are here shown conclusively. The average tensile strength of 49,800 
lbs. per square inch is probably about twice that of the original castings, 
while the average elongation of 6.6 per cent indicates a very considerable 
ductility. This elongation of yV inch to the inch, together with an assumed 
corresponding compression, makes it apparent that small sections would 
submit to a considerable amount of bending distortion and other kinds oi 
abuse before breaking. In other words, the iron is now twice as strong to 
resist a static load, and probably many hundred times as strong to resist the 
force of stocks or blows, as was the original cast iron. 

The elastic limit in compression is very low, but the compressive defor¬ 
mation may be very great. 

The relative strength and ductility acquired under varying periods of 
annealing, from 3 to 9 days, is shown in Fig. 59, where the averages of all the 
results given by Mr. Stanford are plotted, after being reduced to a common 
standard of reference. The few tests on turned-down specimens are also 
plotted, but these are too few to give either very accordant or very trust¬ 
worthy results. 

In Fig. 60 are shown the results of tension tests on malleable cast iron of 
y inch and inch in thickness, and also of ^-inch phites which had been 
welded together. These last show a greater strength than the unwelded 
bars. 

* Due allowance being made for the relative portions of each. 

f These parts should have been dressed in order to prevent any want of symmetry 
in the applied forces, or forms like that shown for cast iron in Chapter XV could have 
been used. Some of the discrepancies in these results are due doubtless to the rough 
surfaces in the grips. 




CAST IRON. 


115 


TABLE VI.-MALLEABLE CAST IRON. 

CHEMICAL COMPOSITION (UNANNEALED AND ANNEALED) AND PHYSICAL PROPERTIES. 


O 

£ 

*3 

a 

v 

X 


391 

395 

400 

406 

4v>*2 

433 

436 

445 

451 

458 

459 
469 
474 
495 
510 


Av. 





o 

a 

o 







O 

■Q 






Unannealed or 

j? 


o 5 





Annealed. 

cS 

o 

go 


Mn. 

Si. 

P. 

S. 



-*-> 

3 

W 

c? 







o 

O 








H 

O 

o 






Before annealing 

3.02 

2.96 

0.06 

0.18 

0.69 

0.138 

0.066 

/ After 

i fc 

2.95 

0.15 

2.80 

0.19 0.69 

0.140 

0.064 


Before 

ti 

3.09 

2.99 

0.10 

0.19 0.60 

0.133 

0.060 


After 

U 

2.98 

0.53 

2.45 

0.19 0.62 

0.130 

0.061 


Before 

l t 

3.09 

2.96 

0.13 

0.18 0.75 

0.142 

0.065 


After 

it 

2.56 

0.31 

2.25 

0.19,0.74 

0.142 

0.061 


Before 

i t 

3.07 

2.77 

0.30 

0.19 0.65 

0.163 

0.064 


After 

t t 

2.91 

0.08 

2.83 

0.20 0.64 

0.164 

0.064 


Before 

it 

3.26 

2.65 

0.61 

0.17 0.69 

0.156 

0.071 


After 

it 

2.95 

0.36 

2.59 

0.18,0.61 

0.151 

0.06S 


Before 

it 

2.85 

2.72 

0.13 

0.18:0.74 

0.161 

0.073 


After 

tt 

2.77 

0.72 

2.05 

0.18 0.72 

0.162 

0.071 


Before 

it 

2.88 

2.73 

0.15 

0.18 0.90 

0.196 

0.069 


After 

ii 

2.58 

0.51 

2.07 

0.1810.87 

0.192 

0.069 


Before 

it 

2.97 

2.75 

0.22 

0.18 0.77 

0.148 

0.073 


After 

ii 

2.66 

0.31 

2.35 

0.19 0.76 

0.145 

0.075 

1 

Before 

ti 

3.08 

2.85 

0.23 

0.18 0.96 

0.123 

0.033 


After 

i( 

2.15 

0.08 

2.07 

0.19 0.96 

0.129 

0.039 


Before 

it 

3.0S 

2.82 

0.26 

0.18 0.74 

0.151 

0.036 


After 

it 

2.03 

0.28 

1.75 

0.18 0.71 

0.150 

0.037, 


Before 

it 

3.03 

2.81 

0 22 

0.190.70 

0.195 

0.038' 


After 

it 

2.06 

0.27 

1.79 

0.20 0.70 

0.192 

0.037 


Before 

ti 

3.09 

3.00 

0,09 

0.20 0.77 

0.127 

0.022 

■ 

After 

it 

2.86 

0.32 

2.54 

0.19 0.75 

0.129 

0.023 


Before 

it 

3.08 

2.92 

0.16 

0.23 0.70 

0.158 

0.023 


After 

it 

2.67 

0.09 

2.58 

0.22 0.70 

0.156 

0.023 

J 

Before 

ii 

2.84 

2.62 

0.22 

0.31 0.63 

0.182 

0.014 

1 

After 

t i 

2.58 

0.06 

2.52 

0.32 0.66 

0.178 

0.018 

- 

Before 

it 

3.26 

3.23 

0.03 

0.40 0.64 

0.136 

0 040 

' 

After 

it 

3.12 

0.53 

2.59 

0.40 0.67 

0.135 

0.039 

t Before annealing 

3.04 

2.85 

0.19 

0.21 0 73 

0.154 

0.050 

| After 

“ 

2 66 j0.31 

2.35 

0.21 0.72 

! 

0.153 

0.050 


Loss of 
Carbon 


j-0.07 

j-0.11 

j- 0.53 
[■ 0.16 
[ 0.31 

j- 0.08 

J 0.30 
[-0.31 
[-0.93 
05 


[° 


.97 


0.23 


K 


41 


-0.26 


0.14 


0.38 


Tests op Annealed Specimens. 


~ ^ cr 

•3 £ rj2 

x t - 

— *3 D 

mco a 


55.100 
43,800 

44.900 
47,000 
45,300 
64,500 

38.900 

69.100 
45,400 
56,700 
44,200 

51.600 

46.600 
4 Q ,100 
46,000 


49,810 


Ter Cent. 

Reduction 

Per Cent. 

Elonga¬ 

tion. 

Number 

of Bars 

Averaged. 

Hours An¬ 
nealed. 

5.5 

5.2 

3 

1C8 

6.1 

6.3 

3 

108 

7.7 

10 3 

3 

108 

7.2 

6.2 

3 

108 

9.1 

8.2 

3 

108 

1.3 

2.8 

3 

108 

4.3 

6.2 

3 

108 

2.6 

4.0 

O 

108- 

7.2 

8.0 

0 

108 

8.4 

8 2 

o 

108 

2.1 

4.2 

3 

108 

r* r* 
i . i 

7.0 

3 

108 

9.8 

8.5 

3 

108 

8.6 

8.7 

3 

108 

5.9 

5.3 

3 

108 

6.23 

6.61 

42 

108 


Note.— The above test-bars were all cylindrical in section and inch in diameter 



Fig. 59._Tensile Strength and Per Cent of Elongation of Cylindrical Test-specimens of 

Malleable Cast Iron in. in Diameter. Figures show Number of Tests averaged for 
each Point Plotted. (Stanford, Tr. Am. Soc. C. E., vol. xxxiv, 1895.) 













































































116 


THE MATERIALS OF CONSTRUCTION. 


In Plate IV the plain bar represents the original form of malleable iron 
from which all the other forms on the plate were worked. In one case it is 



Fig. 60.—Tension Tests of Malleable Cast Iron. Each Curve the Mean of Two or Three 

Tests. (.Berlin Testing Laboratory, 1886.) 

folded over and the ends are welded together, while in another it has been 
forged like wrought iron. All the other forms were bent cold. 




















CHAPTER VIII. 


WROUGHT IRON. 

83. Definition. —Wrought iron may be defined as nearly pnre iron inter¬ 
mingled with more or less slag. As will appear from a study of the methods 
of production to be described, the iron is formed in a bath of melted slag 
(somewhat as butter is formed in churning), and when it aggregates into a 
pasty mass and is removed from the furnace, to be squeezed and rolled, some 
of this slag remains intimately associated with the iron. This gives to 
wrought iron a fibrous appearance (see Fig. 324) not found in any other 
metal.* In the most carefully made iron this fibrous appearance is uniform 
throughout the entire cross-section. It is not uncommon, however, especially 
in the cheaper grades of wrought iron, to find it largely and coarsely crystal¬ 
line. Wrought iron melts only at a very high temperature, and assumes a 
perfectly plastic state through a considerable range of temperature below 
this melting heat, in which condition it is easily and perfectly welded. It 
is more or less ductile when cold, and will not harden when heated and 
quenched in water. 

The oldest methods of production of wrought iron were all direct pro¬ 
cesses, obtaining the malleable product at one operation, or directly from 
the ore. While some modern processes also proceed on this plan, practically 
all the wrought iron of to-day is made from pig iron and various kinds of 
scrap by a puddling process. 

METHODS OF MANUFACTURE. 

84. The Puddling Process Briefly Stated, f—“ The ordinary puddling 
furnace, is a single-bedded reverberatory of simple construction, formed 
externally of cast-iron plates, tied together with wrought-iron rods, and 
provided with suitable openings in front for the fire-hole and the working- 
door, and lined internally with refractory fire-brick. The crown of the 
furnace is also of fire-brick, and is open to the air. The bottom of the 
furnace is composed of three cast-iron plates, which rest upon an iron frame. 
The grate of the furnace has wrought-iron fire-bars, and is large in propor- 


* To develop this fibrous appearance nick a bar of wrought iron on one side and 
bend it double, and if possible split it down like a stick of timber. See Fig. 324. 

f The quoted paragraphs on wrought iron have mostly been taken from Turner’s 
Metallurgy of Iron, Lippincott & Co., 1895. 


117 




118 


TEE MATERIALS OF C0NS1 RUCTION 


tion to the bed or crucible part on account of the very high temperature 
required, particularly towards the end of the process. Each puddling 
furnace is provided with a separate flue, which is either connected to a 
simple rectangular stack, provided with an iron damper, or which passes into 
a boiler-flue so as to economize the waste heat of the furnace. A sectional 
view of such a furnace is shown in Fig. 61. 


% 



.~~ ] 



Fig. 61. —Plan and Section of a Simple Reverberatory Furnace. 

“ Two men are employed at each furnace, and are called the ‘ puddler 9 
and the ‘ under-hand ’ respectively. The work is very laborious, while it 
entails no little skill if good results are to be obtained. Usually six heats 
are worked in a turn of tw r elve hours, but exceptionally seven heats are 
obtained. . . 

“ The furnace is first charged with a sufficiency of fluxing cinder or 
‘ hammer slag ’ (oxide of iron) which has been squeezed out under the 
hammer from previous balls, and there is then introduced about 500 lbs. of 
good gray forge-iron. The door is closed and the charge is then heated to 
melt the iron, and the most favorable results are obtained when the iron 
and the cinder, charged as above described, become pasty, and melt down 
together. "When the iron has thoroughly melted down and has become 
fluid, it is carefully watched until it has ‘ cleared,’ and until a number of 
small blue jets of flame issue from the surface of the liquid. The damper is 
now 4 put down,’ or closed, so as to fill the furnace with a reducing (non¬ 
oxidizing) atmosphere, and to lower the temperature somewhat. In a short 
time the jets of blue flame almost cease, and the mixture of iron and cinder 
rises in the furnace to a height of some 8 or 10 inches, and during this stage 
constant stirring or ‘ rabbling ’ is necessary to prevent the iron settling on 












































































WROUGHT IRON. 


119 


the bottom of the furnace, and to assist the decarburization by bringing the 
(carburized) iron and cinder (iron oxide) into uniform and intimate contact. 
The whole mass should now be in motion, and bubbles of gas should rise and 
burn with a blue flame, tinged more or less with yellow, at the surface. 
When the ‘ boil ’ is thus in full progress, or ‘ well on,’ the damper may be 
raised somewhat, and the iron will soon be observed to ‘ come to nature ’ or 
to separate from the cinder. The first sign of this is the appearance of 
small bright spots on the surface of the cinder, which alternately appear and 
disappear. The cinder now gradually sinks, and leaves the iron as an irreg¬ 
ular mass, not unlike the small globules or grains of butter produced by the 
churn; and as in good butter-making so in good puddling, the grains should 
be small and uniform throughout the mass. The temperature should now 
be raised to the highest point so that the iron may be at a welding heat; the 
puddler after first lifting the metal and turning it over, by inserting a bar 
underneath in order to prevent the bottom becoming colder than the top, 
and breaking it up, proceeds to collect it into balls, which are taken to the 
hammer. ’ ’ 

85. Oxidation in Puddling.—“ The following remarks on the oxidation 
of cast iron under different conditions, will explain the differences between 
the old and newer processes of puddling. 

“ It is usual to speak of atmospheric air as oxidizing and removing the 
impurities present in cast iron, but if a globule of cast iron be melted in the 
air, and then exposed to a blast of air or oxygen, it will be observed that the 
impurities are not the only substances that are oxidized. It is true that 
under very special conditions either the carbon or the silicon may be 
separately oxidized. But on performing the experiment above indicated it 
will be found that the iron itself is oxidized in about the same relative pro¬ 
portion as the other elements, and the result is that practically a layer of 
impure magnetic oxide of iron is formed outside the globule, while the por¬ 
tion of metal that is left is of nearly the same composition as the original 
iron. If the cinder be allowed to.run away as rapidly as it is formed, ulti¬ 
mately the whole of the iron would be converted into magnetic oxide, and 

4 / 

the last particles of cast iron so removed would have nearly the same com¬ 
position as the original metal. In this case oxidation has taken place, hut 
no purification has resulted. 

“ If, now, the same experiment be tried, but the fluid oxide be allowed 
to remain, and to cover the fused metal, the oxidation of the iron will pro¬ 
ceed very little further; a reducing action will then be commenced whereby 
the silicon, carbon, and other easily oxidizable elements will be removed, 
but at the same time a corresponding weight of iron will be returned to the 
globule from the surrounding slag. 

“ xf, thirdly, a globule of cast iron be covered with magnetic oxide of 
iron to protect it from the air and to supply the necessary cinder, and it be 
then strongly heated, it will be found that the globule has not lost in weight, 
but has become distinctly heavier during the process. It is scarcely neces- 


120 


THE MATERIALS OF CONSTRUCTION. 


sary to say that the waste which takes place daring reheating or remelting,, 
corresponds to the first condition above given. The oxide runs away as it is- 
formed, and this is an example of waste of iron pure and simple. The only 
redeeming feature is that sometimes the oxide produced may be of value for 
other purposes. The early open-hearth processes for producing wrought 
iron in fineries, and the original method of puddling, resemble the second 
case, for part of the iron is wasted to produce the cinder needed to remove 
the impurities from the remainder of the metal. The larger the proportion 
of these impurities the greater will be the loss of iron necessary to make the 
required cinder, and for this reason a comparatively pure iron is needed, in 
order to obtain the least waste, while at best the waste is comparatively 
great. A deficiency of fluid cinder in the early stages of ordinary puddling, 
or pig 4 boiling,’ has an exactly similar effect, and leads to waste for the 
same reasons, 

44 In the modern method of working, on the other hand, the object is to 
imitate the conditions of the third case previously supposed. Oxide of iron 
can be bought much more cheaply than it can be made from pig iron, and 
besides the oxidation of pig iron requires the expenditure of time and fuel. 
Oxide of iron is, therefore, supplied in its cheapest and most readily available 
form, and as much of this oxide as possible is reduced and converted into 
wrought iron. To do this it is necessary that the iron and fluid oxide 
should be brought into actual and frequent contact, and so perfect fluidity 
and constant rabbling are needed. There is, of course, a practical limit to 
the amount of carbon which can be present, due to the fact that cast iron 
cannot take up more than a certain amount, say 4 per cent, of this element. 
There is also a practical limit in the case of both silicon and phosphorus; 
the first being regulated by the increased consumption of time and fettling 
with excess of silicon, and the second being determined by the inferior 
quality of iron produced, with large proportions of phosphorus. But within 
these practicable limits it is advantageous to reduce as much of the oxides 
of iron supplied as possible.” 

86. Details of the Puddling Process.— 44 The working heat of puddled 

iron may be conveniently divided into four stages, which will be separately 
described, namely: 

44 (1) Melting-dozen stage , lasting about half an hour, by the end of 
which most of the silicon and manganese and a considerable proportion of 
phosphorus have been removed. 

44 (2) Quiet fusion or 4 clearing ’ stage, lasting about ten minutes, 
during which the rest of the silicon and manganese and a further quantity 
of phosphorus are removed. 

44 (3) The boil , which lasts nearly half an hour, during which the greater 
part of the carbon is eliminated, together with a further quantity of phos¬ 
phorus. 

44 (4) Balling-wp stage , which occupies some twenty minutes, and by 


WROUGHT IRON. 


121 


which time the purification, except as regards the removal of slag, has prac¬ 
tically ceased. 

“ 1. The furnace having been suitably prepared, and hot from a previous 
heat, the pig iron is charged as before described; the door is then closed, and 
the working opening in the bottom of the door covered with an iron plate 
and rendered as far as possible air-tight by means of a little fine cinder 
thrown with the shovel. The fire is also made up, and heating proceeds for 
some twenty minutes, by which time the top of the pig iron is red-hot, and 
the flux begins to soften. The pigs are now turned so as to heat them more 
uniformly and the door is again closed; in a few minutes the iron begins to 
melt, and if carefully watched may be seen to trickle down into the cinder 
in drops. The workman now introduces an iron rod, stirs up the mass, and 
brings up any pieces of iron which have not completely melted, and which 
might otherwise remain covered and take longer to melt. When the whole 
is thoroughly fluid and well mixed the melting-down stage is finished. 

44 2. One of the workmen, generally the under-hand, now introduces a 
bar which is bent at the end at right angles, and so acts as a scraper or 
stirrer, and the whole charge is well stirred and exposed to the action of the 
fettling and cinder, and also to some extent to the oxidizing influence of the 
a.ir. The temperature is maintained as high as possible during this stage. 

“ The fron is thus thoroughly 4 cleared ’ or purified from silicon, the 
point at which clearing is completed being judged by the appearance of the 
charge, and upon the skill of the workman at this stage much of the subse¬ 
quent success depends. 

“ 3. When the metal has cleared, and is in a state of tranquil fusion, the 
next point is to bring on the 4 boil.’ The puddler, therefore, diminishes the 
draught, or 4 puts his damper down,’ so as to fill the furnace with a smoky 
flame and lower the temperature. In some cases also the door is opened and 
water thrown in at this stage, as this promotes rapid cooling and supplies 
oxygen at the same time. The (carbonized) metal being thus somewhat 
thickened, and being vigorously stirred during the whole time, becomes 
intimately mixed with the (iron oxide) cinder; the carbon is thus oxidized, 
producing carbon monoxide, which burns in blue flames as the bubbles of gas 
rise and burst. These flames are sometimes called 4 sulphur ’ or 4 puddler’s 
candles,’ on account of their pale blue color. The charge thus swells up and 
rises some six inches in the furnace (like boiling molasses), and as the heat 
increases and the damper is opened somewhat, a quantity of red-hot slag 
flows over the fire-plate (at the door) into a cast-iron slag-wagon placed 
ready to receive it. The violence of the action now gradually diminishes, 
the iron 4 comes to nature,’ and the charge settles in the furnace; the less 
fusible wrought iron is in the form of a porous cake, and the residue of slag 
collects chiefly underneath. 

44 4. In the fourth, and last, stage the puddler has to manipulate the 
iron into convenient forms for subsequent treatment. For this purpose the 


122 


TUE MATERIA LIS OF CONSTRUCTION. 


cake of metal is broken up by inserting a bar underneath, and is worked at 
a welding heat into one uniform mass or ball. This is now divided into 
about six balls, of approximately equal size, each of which weighs about 80 
lbs., and these are in turn withdrawn from the furnace and taken to the 
hammer, where the slag is to a great extent expelled, and a bloom of iron is 
obtained. This is rolled, without reheating, into ‘puddled bar,’ which is 
the name given to the crude wrought iron produced as above described.” 

87. Production of Muck Bars.— 44 The balls of crude wrought iron, hav¬ 
ing been produced in the puddling-furnace as before described, have now to 
be compressed to expel the slag and render the material more uniform in 
character; they are afterwards rolled into bars, which receive the name of 
‘ muck bars.’ For compressing the iron various forms of hammers or 
squeezers are used, while for the production of bars, grooved rolls, as intro¬ 
duced by Oort in 1783, are generally employed, though in a few exceptional 
cases, where water-power is available, bars are still produced by the hammer 
or 4 battery,’ as in ancient times. 

44 Various forms of squeezers have been introduced from time to time, 
chiefly with the object of preventing the jar or shock due to the action of the 
hammer, though such appliances have not met with very general application. 
The more usual forms may be conveniently divided into two classes: 

44 (1) Those in which compression is produced by means of m lever, as in 
the 4 alligator ’ or 4 crocodile ’ squeezers, which are so called by the workmen 
from the resemblance between the motion of this class of squeezer and that 
of the mouths of the animals above mentioned. 

“ (2) Those in which a revolving cam is employed.” 

The principal machine of this class is the Burden Squeezer, which has 
come into very general use in the United States. This consists of a fluted 
cylinder mounted eccentrically within a fluted cylindrical casing. The 
inner cylinder is made to revolve, and the puddle-ball is dropped between 
the moving cylinder and the fixed casing, on the side of the larger opening, 
whence it is slowly rolled around through the smaller space on the opposite 
side, during which process the slag is effectually squeezed out of it. On 
emerging again into the larger part of the annular space it has been reduced 
to a form suitable to put into the rolls. 

In Silesia hydraulic pressure was introduced in 1897 for removing the 
slag, and with great success.* 

44 The iron, having been thus compressed and consolidated by some form 
of hammer'or squeezer, and a considerable portion of the slag expelled, is 
now taken while still hot to the puddle-rolls, where it is converted into bars. 
The bars are allowed to cool, and are afterwards cut up with shears into 
suitable lengths; these are then made into bundles, or 4 piles,’ of the required 
weight and size. When a specially smooth surface is required, as in the 
production of sheet iron, it is usual to make the top and bottom of each pile 
of 4 scrap bars ’; these are made by reheating the crop ends of finished bars 
or other good wrought-iron scrap, and are therefore more uniform in char- 


* See Stahl u. Eisen, vol. xvii. p. 257. 




WROUGHT IRON. 


123 


acter, and possess a smoother and cleaner surface than ordinary puddled 
iron.” 

88. Reheating the Muck Ears. —“ The puddled iron having been pre¬ 
pared as before described, is now taken from the forge to the other part of 
the works, which is known as the ‘ mill.’ This is usually covered with a 
tolerably lofty roof, but is open at the sides; it contains reverberatory furnaces 
for heating the piles of puddled iron, and also rolls of various sizes, with the 
necessary engine and connections required for producing the various ‘ sec¬ 
tions ’ of finished iron. A steam-hammer is also provided if forgings are 
produced, bat otherwise this is not required. 

“ The temperature employed in mill-furnaces is a white heat, and suffi¬ 
ciently high to cause the metal to weld together when it is passed through 
the rolls, to which it is taken from the furnace.” 

89. Rolls.— “ The rolls used in iron-works are classified according to 
their shape and the method adopted in their production. They are gener¬ 
ally made from a strong close-grained cast iron, usually that obtained from a 
blast-furnace, in which cold blast is employed. Occasionally steel rolls are 
used, and these appear to be somewhat growing in favor in recent years. 

“ Rolls may be classified according to their shape into— 

“ (1) Flat or plain rolls , which are used for rolling sheets or plates. 

“ (2) Grooved rolls , which are required for the production of bars, rods, 
angle and channel iron. 

“ According to their method of production rolls are classified as— 

“a) Grain rolls , which are produced in moulds of green or dry sand, 
and in which the surface of the roll after turning down shows the ordinary 
grain of the cast iron from which it is made. These are used for all rough¬ 
ing purposes and for sections, and in other cases if the metal is finished hot. 

“ (2) Chilled rolls , which are produced in cast-iron moulds or chills. 
They, therefore, have a hard white surface of chilled iron, which varies in 
thickness from about £ to f of an inch, according to the size of the casting 
and the class of work for which it is intended. Rolls of this kind are more 
costly, and are employed for the production of sheets, plates, or strip, or 
in other cases where specially fine surfaces are required.” 

Small rolls tend more to elongate than to spread the materials, while 
large rolls tend both to elongate and to spread the metal. 

90. Effect of Repeated Reheating of Iron. —“As it is well recognized 
that puddled iron is much improved in quality by being cut up, piled, 
reheated, and rolled or hammered, and that the iron is further improved 
by repeating the operation, it might be assumed that by continuing this pro¬ 
cess the properties of the metal might be again and again further improved. 
In practice, however, this is not found to be the case, and it is only in 
special cases that it is advantageous to reheat puddled iron more than twice. 
It has been shown by experiments, in which puddled bar was reheated and 
rolled as many as twelve times, that after about six workings the metal began 
to seriously deteriorate, and even in the earlier workings, aftei the third no 


124 


THE MATERIALS OF CONSTRUCTION. 


corresponding advantage was obtained for tlie fuel and labor expended and 
the waste incurred. The results obtained were as follows (Useful Metals y 
p. 318): 

Tensile Strength in 
Pounds per Square Inch. 


Original puddled bar. 43,900 

2d working. 52,860 

3d “ 59,580 

4th “ 59,580 

5th - 57,340 

6th “ 61,820 

7th “ 59,580 

8th “ 57,340 

9th “ 57,340 

10th “ 54,100 

11th “ 51,970 

12th “ 43,900 


“If it be assumed that the result in the fifth heating was accidentally 
low, it will be seen that all the other tests follow in a regular succession, the 
maximum tensile strength being obtained with the sixth working. Probably 
with iron of different composition or character the maximum would be 
reached at a different point, but in all cases the gradual original improve¬ 
ment and subsequent deterioration would be observed. When the metal 
passes into the hands of the smith it is found that if it has been worked 
during its previous preparation so as to bring it to its best condition, it has a 
tendency to c go back ’ in forging; while, on the other hand, if the iron has 
not been unduly worked, it improves when properly smithed. For this 
reason also it is not advantageous to often reheat and work iron during the 
process of manufacture, and ‘ best,’ ‘ best best,’ or ‘ treble best ’ irons are 
obtained, not by frequent heatings, as is sometimes stated, but by the careful 
selection of all the materials employed, and by systematic and frequent tests 
of the iron during the various stages of manufacture.” 

91. Sections of Finished Iron. —“ The shape into which finished iron is 
rolled varies according to the purposes for which it is designed, the chief 
divisions being plates, sheets, strips, bars, angle-irons, and rails, the last being 
relatively of much less importance than formerly. Among the more usual 
shapes or ‘ sections ’ may be mentioned the following: bars, including round, 
half-round, square, flat, round-edged flats, oval, octagon, together with 
levelled and bulb iron, and rods; tee (or T-shaped) iron, tee with round top 
or edges; angle- (or L-shaped) iron, angle-iron with unequal sides or round 
back; channel-iron, I iron, Z iron; rails, including single-headed, double¬ 
headed, and flange; and horseshoe-iron, which is rolled single-grooved, 
double-grooved, or concave. Numerous other forms are also required from 
time to time for various purposes; so that the number of rolls which have to 














WROUGHT IRON. 


125 


be kept in stock at a large works with a general trade is very great, not 
nnfrequently amounting to hundreds. As each pair of rolls is generally only 
capable of finishing one section of iron, the cost of the supply and main¬ 
tenance of rolls forms a considerable item of the expenditure of an iron¬ 
works. ’ ’ 

92. Imperfections in Finished Iron.— 44 The three chief varieties of 
imperfection in the appearance of finished iron are rough edges, spilly 
places, and blisters. 

44 (a) Rough edges , when not due to imperfections in the rolls or to care¬ 
less working, are a sign of red-shortness, and are particularly noticeable m flat 
bars or strips. Red-shortness may be due to an excess of carbon, or to the 
presence of sulphur, particularly if copper is also present. Usually, how¬ 
ever, if iron has been properly puddled, practically the whole of the sulphur 
is eliminated, and the red-short condition is due to the 4 dryness ’ of the iron. 
Iron is said to be dry when it is deficient in fusible or welding cinder, which 
may be readily squeezed out from between the particles when the iron is 
worked, and so enable clean surfaces to be brought together to form a good 
weld. A thick dry cinder, on the other hand, leads to red-shortness, and a 
piece of brick or other foreign matter which crushes up in the rolls to form 
a dry powder acts in the same manner. 

44 (b) Spilly places are spongy or irregularly spotted parts which are not 
unfrequently noticed in sheets, and which are occasionally met with in all 
kinds of wrought iron. They are generally due to imperfect puddling, 
whereby one part of the iron, when 4 coming to nature,’ has been oxidized 
more than another. If the heat has been thoroughly well worked and the 
iron uniformly mixed, spilly places are seldom observed. 

44 (c) Blisters are not unfrequently met with in sheets, and lead to con¬ 
siderable loss and inconvenience. They are much less common in steel sheets 
than in iron, and some experiments conducted in 1893 led the author to 
attribute the formation of blisters to a reaction between carbon and oxide of 
iron in wrought iron of inferior quality. This vdew is in accordance with the 
experiments of A. Friedmann, who collected and analyzed the gas contained 
in a number of blisters. This gas was found to contain over 70 per cent of 
carbon monoxide, the remainder being chiefly carbon dioxide, with some 
nitrogen and hydrogen. Inside the blisters a quantity of scaly matter is 
found, which Friedmann states to consist of about two thirds silica and 
nearly one third iron aluminate (FeA10 3 ), together with small quantities of 
other oxides. ’ ’ * 

MECHANICAL PROPERTIES OF WROUGHT IRON. 

93. Crystalline Fracture.—As explained in Art. 84, the fibrous appear¬ 
ance of wrought iron when nicked and bent with a splitting action, similar 
to that of a piece of timber treated in like manner, is due to the presence of 


* Inst. Journ., 1885, vol ii. p. 645. 





126 


THE MATERIALS OF CONSTRUCTION. 


tlie foreign matter which formed the slag or bath from which the puddled 
ball was taken. Ordinarily when wrought iron is broken in tension in a test¬ 
ing-machine the fracture appears to be wholly fibrous, somewhat like that 
of soft steel, but with a darker and more ragged appearance. If a wrought- 
iron bar be nicked and broken by bending, it will usually show a fibrous 
appearance, whereas steel so treated will always show a crystalline fracture. 
Occasionally, however, a part of all of the fracture of a test specimen of 
wrought iron, whether broken in tension or by nicking and cross-bending, 
will have a coarsely crystalline fracture. It is very common, also, to find 
such a fracture when wrought iron breaks in service, as in the case of car and 
wagon axles, steam-engine cranks and pins, etc. In such cases as these it 
has been common to ascribe the failure to the crystallized condition of the 
iron and to assume that the iron had changed to this condition in service. 
This is called the theory of the cold crystallization of wrought iron. Those 
w r ho believe in it usually ascribe the change to a vibratory action. Whether 
or not wrought iron ever does crystallize in service in this or in any other 
manner has been a disputed question for the last half-century. It has, 
however, remained a theory the truth of which has never been established 
by actual experiment, and it is now one which seems to have no scientific 
adherents. It has, however, become so thoroughly fixed in the minds of the 
less educated users of iron and steel that it is met with on every hand, and 
this action is stated to be a fact with the most positive assurance by nearly 
all mechanics and is commonly believed by the public generally. The views 
of the author of this work on this subject may be summarized as follows: 

I. The normal molecular arrangement of wrought iron is crystalline, but 
the thorough admixture of the inert slag in a well-worked product prevents 
these crystals from forming in visible sizes. The ordinary fibrous fracture, 
therefore, exhibits rather a lateral view of these finely crystallized threads, 
thus causing this to present a fibrous appearance. 

II. When any portion of the puddled ball as removed from the furnace 
is not intermixed with foreign matter, as may be the case from overheating 
and melting of some portion of the puddled ball, or from the inclusion in the 
mass of some unreduced melted cast iron, these portions being really of the 
nature of ingot metal or steel, rather than of wrought iron, then these 
masses of iron, free from foreign matter, when somewhat cooled and rolled 
into a bar, will form in that bar a part of the cross-section which will be able 
to crystallize on a slow cooling in large-sized crystals, so as to be clearly visible 
to the naked eye. When such melted portions are due to overheating of 
the puddled ball the iron is said to be burnt, but a too-rapid hurrying of the 
boding process under a low heat will also enable some of the unreduced cast 
iron to be removed from the furnace in this way with a similar result. 

III. With the ordinary and. more inferior grades of wrought iron now on 
the American market, it is very common to find large portions of the cross- 
section of test-bars showing a crystalline appearance, even for tension-test 
specimens of standard form. Much more, therefore, are such irons likely to 


WROUGHT IRON. 


127 


have this appearance when nicked and broken across, or when nicked and 
pulled in tension. 

I\ . All wrought iron when broken with extreme suddenness will show a 
crystalline fracture. This is because time is not given for the drawing out 
of the section, rupture occurring directly across the fibres, so that the frac¬ 
ture shows only the end view of the same. 

V. \\ hen a bar is nicked with a sharp chisel, or grooved in a lathe with 
a sharp-pointed tool, and broken across, rupture begins at one side without 
any elongation of the fibres, and extends from fibre to fibre across the section 
in such a way as to produce a result similar to that caused by an instan¬ 
taneous rupture cited in IV. In this way wrought iron will often show a 
crystalline or granular fracture, when under the ordinary tensile test it 
w r ould be wholly fibrous. All steel or ingot metal will always show a 
crystalline fracture when treated in this manner, although for all the soft 
and medium grades of steel the fracture is always fibrous or silky when 
broken in tension, with the usual accompanying elongation and contraction. 

VI. Much of the so-called wrought iron on the market to-day consists 
simply of rolled fagots of “scrap-iron,” a large portion of which is really 
scrap-steel. As these are heated only to a welding heat, and then rolled into 
merchant bar, there is no real mixing of the metals, and the several com¬ 
ponents form so many separate portions of the cross-section of the final rolled 
forms. The crystallized steely areas found in the fractures of most wrought 
irons of the common grades to-day can be largely traced to this source. 
Wrought-iron railway-axles and other large forms are usually made up in 
this way. 

VII. When wrought iron breaks in service, therefore, and shows a 
coarsely crystalline fracture, it does not prove that crystallization has 
occurred in service. It proves only that this iron had such a structure 
originally. If, however, the rupture occurs in practice in a suddenly con¬ 
tracted area, as in a screw-thread or in a sharp angle, or if it has been jwo- 
duced with extreme suddenness, as in case of an explosion or shock of any 
kind, if the appearance of the fracture is finely crystalline or granular, this 
appearance may be wholly due to the method of failure. This is shown by 
the fact that if a specimen be cut from the adjoining metal and tested in 
tension with the standard form of specimen, it might show a wholly fibrous 
fracture. In such cases, therefore, the crystalline appearance of the fracture 
is due to the particular conditions as to shape of specimen and suddenness of 
rupture and not to any molecular change which has taken place in the iron.* 

* From the Report of U. S. Watertown Arsenal Tests of Metals for 1890, in which are 
recorded many tests of specimens cut from the journals of old railway-axles, the follow¬ 
ing note is taken : 

“Axles have been examined which have had long-continued service, the journals of 
which showed incipient cracks, indicating that rupture had begun and that further use 
must result in complete rupture. It is a remarkable fact that the tests of the metal of 
these journals near these cracks showed no loss of strength or ductility. No indications 




128 


TUE MATERIALS OF CONSTRUCTION. 


94. The Welding of Wrought Iron.— It is a peculiar property of wrought 
iron that it remains in a plastic condition throughout a considerable range of 
temperature. If two pieces of wrought iron could be reduced to this plastic 
state (a white heat) with perfectly clean surfaces, and pressed together 
firmly and allowed to cool, the union would be so perfect as to be practically 
as strong as any other portion of the material. The great difficulty in suc¬ 
cessful welding lies in the fact that when the iron is heated in the presence 
of oxygen the surface is oxidized, and this oxide of iron, being quite fusible 
at this temperature, forms a complete coating of slag over the entire surface. 
When two such surfaces are brought together, therefore, each being entirely 
covered with melted iron oxide, which is practically a foreign substance, the 
union effected is necessarily imperfect. The degree of imperfection depends 
on the amount of this melted slag which succeeds in remaining in the joint. 
In order to remove this liquid slag as much as possible, the tivo surfaces 
should he convex to each other when they are brought together. That is to 
say, they should first come in contact along the central portion of the weld 
area, so that the hammering or the pressure by which the weld is effected 
will, as perfectly as possible, squeeze out this liquid slag from the joint, thus 
allowing the plastic iron surfaces to come into immediate and actual union. 
If any portion of this melted oxide remains in the joint, it entirely prevents 
a union of the surfaces over such area as it occupies, and to that extent 
weakens the joint. As it is impracticable to heat the surfaces to be welded 
or even to join them in a vacuum, or away from the oxygen of the air, it is 
impossible to avoid entirely the presence of the melted oxide of iron in weld¬ 
ing operations. With intelligence and care, however, in the performance of 
the work, nearly all this oxide can be removed in the act of welding, and a 
practically perfect union effected. To assist in removing this melted oxide, 
borax is commonly used. This being a perfect solvent of the oxide, the 
wdiole is changed to a thin liquid, which is the more perfectly squeezed out 
of the joint in the welding process. In this way steel may be welded which 
would not unite without it. When the parts to be joined are heated in an 
ordinary forge the blast of air causes an excessive oxidation of the surfaces, 
and thus gives rise to large quantities of the melted slag. By maintaining 
a thick fire most of the oxygen has been consumed to CO or C0 2 before 


of a tendency to crystallize were discovered, and inasmuch as the metal has gone 
through all the phases of deterioration up to the limit of actual rupture without showing 
a crystalline tendency, it is thought this demonstrates and proves that this material is 
incapable of cold crystallization when exposed to the conditions of service.” 

In one instance one of the old cracks which had developed at the inner shoulder of 
the journal reached to a depth of 0.02 inch into the side of the test specimen, and yet 
the specimen broke two inches from this'section. After rupture the end of the specimen 
(1£ in. diam.) containing this crack was bent cold 33 degrees with “ this crack at the 
middle of the bend on the tension side, which opened the crack in width and also 
developed numerous cracks in this vicinity,” but without rupture. All the tests showed 
fibrous fractures. 



WROUGHT IRON. 


129 


reaching the iron, and hence less oxide is formed. If the parts were heated 
in a reverberatory furnace or in a “ muffler,” raised to a sufficient tempera¬ 
ture and kept out of the way of air-currents, a much less amount of this slag 
would be formed, and the welding would be more readily performed. One 
of the advantages of electric welding lies in the fact that no air-current is 
employed, and by having the parts in contact during the time they are being 
heated, the air is largely excluded from the welding surfaces, and hence 
little or no oxide is formed there to prevent a perfect union. It is largely 
for this reason that electric welding may be more perfect than hand welding. 

In view of the inherent difficulties described above, it might well be 
anticipated that welded joints are necessarily very unreliable even when done 
with more than ordinary care. Many tests of the strength of welded joints 
have shown that this strength may be anywhere from 30 to 100 per cent of 
the strength of the parts which have been joined, and in the hands of careless 
or incompetent workmen the strength of a welded joint may be almost zero. 
With the most careful work, however, that is found to be practicable in the 
best forging practice, the average strength of hand-welded joints has been 
found by Kirkaldy * to be in the case of round iron tie-bars from 1 j- to 3^ 
inches in diameter, but GO per cent of the average strength of the bars. In 
the case of flat plates from 2J to 6 inches in width and from £ inch to 1 
inch in thickness, the average strength of the welds was 71 per cent of the 
strength of the plates. In the case of chain-link welds from 4 to 2| inches 
in diameter, the average of 216 tests showed an average strength of the welded 
joints of 83 per cent of the strength of the iron rods. In the case of a 
wielded chain, where the strength of the chain is only that of its weakest link, 
it would not be safe to rely on a strength of joint greater than 50 per cent 
of the strength of the iron from which the chain has been made. 

In 1885 Professor Bauschinger undertook an elaborate series of experi¬ 
ments to determine the relative welding qualities of soft steel and wrought 
iron, also the relative efficiencies of forging by hand and under a steam- 
hammer. The results of his experiments have been condensed in the 
following tables. These results show a strength of welded soft-steel bars 
equal to 89.2 per cent of the strength of the original material, while the 
efficiency of the welds of the wrought-iron bars was 95.6 per cent. The 
relative value of hand and power forging is indicated in the second table, 
wdiere it is shown that the hand forging gave an efficiency of 84 per cent, 
while the steam forging gave an efficiency of 97.2 per cent, on the soft-steel 
bars, while on wrought iron these were 87.9 per cent and 91.0 per cent 
respectively. 

These tests were made under the most favorable conditions, and they 
probably represent the highest attainable efficiency in welding on both kinds 
of materials. These results should, therefore, not be taken as representing 
average results in practice, but rather as an ideal which may possibly be 


* Kirkaldy’s System of Mechanical Testing , London, 1891, report KK. 




JO JO 


130 


TEE MATERIALS OF CONSTRUCTION. 


reached with the greatest care. It will be noticed that the fourth soft-steel 
specimen gave an efficiency of 99.6 per cent, the break occurring entirely 
outside of the weld; while the sixth set of specimens of soft steel gave an 
efficiency of but 57.3 per cent, the break occurring in the weld. Another 
specimen of soft steel would not weld at all. 

TABLE VII.—BAUSCHINGER’S TESTS OF THE STRENGTH OF WELDS 
WITH LOW-CARBON STEEL (INGOT IRON) AND WROUGHT IRON, 

(Each line of “ welded results contains the mean of two tests.) 

SOFT STEEL OB INGOT IRON 


Dimen¬ 
sions of 
Original 
Cross- 
section 
in Inches. 

Cross-sect ion 
of Test-bar. 

Condi¬ 
tion of 
Bar. 

Method of 
Welding. 

Yield-point. 

r* 

it 

C 

2- 

72 

V 

"m 

c 

’ -A 

£ 

c 

-4- 

c 

p 

"3 

’3) 

o 

5 

J 

t 

Percentage of Elon¬ 

gation for 10 Inches. 

i 

v . 
Ph sS 

P 

C< 

a o 
blZ. 

5 5 

— w 

0> y 

u - 

Is w 
P-4 

Remarks. 

Dimen¬ 

sions. 

Area. 

3.15x1 18 

2.19x0.72 

1.58 

> 

Orig. 

One heat 

39,100 

61.860 



31.3 

59 


3.15X1.18 

2.26x0.71 

1.60 

Welded 

Steam hammer 

38 390 

58,940 

95.3 

12.8 

14 

Both broke in weld 

3.15x0.98 

2.17X0.72 

1.56 

Orig. 

One heat 

35.230 

59,580 



28.2 

50 


3.15x0.98 

2.11x0.71 

1.50 

Welded 

Steam hammer 

38,100 

62.560 

10 

5.0 

12.5 

13 

Both broke in weld] 

1.77X0.87 

0.98x0.72 

0 71 

Orig. 

One heat 

42,669 

69.240 



23.1 

42 


1 77x0.87 

1.07X0.70 

0.75 

Welded 

Steam hammer 

44 790 

70,740 

10' 

2 2 

13.1 

15 

Broke in weld 

1.34X0.59 0 58x0.59 

0.34 

Orig. 

Two heats 

43.650 69.100 



24.7 

52 


1.34X0.59 

0 64X0.54 

0.35 

Welded 

Hand forging 

38,390 

68,820 

99 6 

17.2 

48 

Broke outside of weld 

1 26x9 55 

0.55x0.55 

0.30 

Orig. 

Two heats 

42,660 

05.400 



29 8 

65 


1.26x0.55 

0.60x0.54 

0.32 

Welded 

Hand forging 

34,840 

60,640 

92.7 

15.4 

68 

Broke outside of weld 

1.18X1.18 

sa¬ 

il 

o 

O ' 

0.39 

Orig. 

Two heats 

46.640 

69,960 



22.8 

42 


1.18x118 


0.39 

Welded 

Hand forging 

36,970 

40,100 

57.3 

0 

0 

Broke in weld 

d = 1.10- 

d = 0.70 

0.39 

Orig. 

Two heats 

33,840 

61,570 



11.9 

15 


d = 1.06 

d = 0.61 

0.33 

Welded 

Hand forging 

35.550 

45,790 

7 

4.4 

0.9 

6 

Broke in weld 

d = 0.79 

d = 0.44 

0.15 

Orig. 

Two heats 

44.080 

66,830 



23.2 

67 


d = 0.79 

d = 0.44 

0.15 

Welded 

Hand forging 

39,100 

58,230 

87.1 

8.7 

17 

Broke in weld 


Average = S9.2 


WROUGHT IRON. 


3.27x0.71 

3.27x0.71 


.56X1 06 
.56X1.06 


1.65X0,47 

1.65x0.47 


1.34X0.63 

1.34x0.63 


1.02X1.02 
1.02x1 02 


d - 1.02 
d =• 1 02 


2.39x0.71 

2.36x0.59 

1.70 

1 39 

Orig. 

Welded 

Three heats 
Steam hammer 

32,700 

24,170 

52,600 

50,050 

95.1 

26.1 

13.4 

42 

23 

Broke in weld 

1.64x0.72 
1.65x0.69 

1.18 

1.14 

Orig. 

Welded 

One heat 

Steam hammer 

22,750 

22,750 

50,050 

50,050 

100.0 

28.5 

20.9 

45 

34 

Broke in weld 

0.8-4X0.47 
0.86x0.43 

0.40 

0 37 

Orig. 

Welded 

Two heats 

Hand forging 

27.730 

22,750 

51,190 

48,910 

95.6 

11.4 

8.1 

18 

14 

Broke in weld 

0 58x0.64 
0.68x0.58 

0.37 

0.40 

Orig. 

Welded 

Two heats 

Hand forging 

28,440 

27,020 

56,880 

55,450 

97.5 

24.3 

15.3 

42 

Broke in weld 

d = 0.59 
d — 0.59 

0 27 
0.27 

Orig. 

Welded 

Two heats 

Hand forging 

29,860 

28,440 

55,030 

56.310 

102 3 

21.5 

15.6 

39 

17 

Broke near weld 

d = 0.59 
d = 0 59 

0.27 

0.27 

Orig. 

Welded 

Two heats 
Hand forging 

29.860 

27,020 

61,000 

50,620 

83 0 

18.3 

9.2 

36 

16 

Broke in weld 


Average = 95.6 

























































































































































































WROUGHT IRON. 


131 


TABLE \ III. BAUSCHINGER^S TESTS OF THE RELATIVE VALUE OF 

HAND AND STEAM FORGING. 

(Welding Low-carbon Steel and Wrought Iron.) 

SOFT STEEL OR INGOT IRON. 


Dimen¬ 
sions of 
Original 
Cross- 
section 
in Inches. 

Cross-section 
of Test-bar. 

Condi¬ 
tion of 
Bar. 

Method of 
Welding. 

Dimen¬ 

sions. 

Area. 

1.26x0.4? 

0.81x0.41 

0.33 

Orig. 


1.26x0.4? 

0.82X0.36 

0.30 

Welded 

Hand forging 

1.26X0.4? 

0.80X0.35 

0.28 

Welded 

Steam hammer 

0.75x0.75 

d = 0.43 

0.14 

Orig. 


0.75X0.7.5 

d = 0.43 

0 14 

Welded 

Hand forging 

0.75X0.75 

d = 0 43 

0.14 

Welded 

Steam hammer 

d = 1.02 

d = 0.59 

0.2' 

Orig. 


d = 1.02 

d = 0.58 

0.27 

Welded 

Hand forging 

d = 1.02 

d = 0.58 

0.27 

Welded 

Steam hammer 

d = 0.91 

d = 0.51 

0.21 

Orig. 


d = 0.91 

d = 0.51 

0.21 

Welded 

Hand forging 

d = 0.91 

d = 0.51 

0.21 

Welded 

Steam hammer 


Yield-point. 

Tensile. Strength. 

Ovighml 

Welded . 

Percentage of Elon¬ 

gation for 10 Inches. 

Percentage of Re 

duction of Area. 

Remarks. 

Broke outside of weld 
Broke outside of weld 

42,660 

47,200 

47,490 

68,110 

68,250 

71,100 

100 2 
104 o 

23.9 
15.7 

20.9 

66 

66 

62.5 

45,640 

66,260 



21.7 

68 


44,220 

61,710 

93.1 

9.1 

9 

Broke in weld 

39.810 

65,550 

98 9 

13 0 

36 

Broke in weld 

42,230 

62,700 



22.9 

63 


24,880 

27,300 

43.5 

0.1 

1 

Broke in weld 

33,130 

54,600 

87.1 

6.9 

18 

Broke in weld 

49,200 

69,530 



23.0 

62 


44,930 

68,960 

99.2 

15.8 

28.5 

Broke in weld 

44,930 

68,400 

98.4 

14.8 

20 

Broke outside of weld 


Average hand forging =84.0 
“ steam “ =97.2 


WROUGHT IRON. 


d = 1.02 
d = 1.02 

d = 0.58 
d - 0.58 

0.27 

0.27 

Orig. 

Welded 

Hand forging 

24,880 

24,880 

55,460 

48,770 

87.9 

23.1 

9.9 

41 

10.5 

Broke in weld 

d = 1.02 

d = 0.58 

0.27 

Welded 

Steam hammer 

27,020 

50,480 

91.0 

12.7 

35 

Broke outside of weld 


95. The Effect of Reduction in the Rolls on the Strength of Wrought 
Iron.* —Other things being equal, the strength of wrought iron will vary 
directly with the amount of reduction in the rolls from the size of the pile to 
that of the finished specimen. If it is desired to obtain an equal strength 

TABLE IX.—EFFECT OF VARYING REDUCTION IN THE ROLLS ON THE 

STRENGTH OF WROUGHT IRON. 


Diameter. 

Length. 

Elastic Limit. 

Ultimate Strength. 

Per Cent of 
Elongation. 

Ratio of Elastic 
Limit to Ulti¬ 
mate Strength. 

1 

4.75 

38,000 

57,533 

17.1 

66.1 

H 

6.25 

34,600 

54,850 

21.65 

62.9 


7.50 

32,600 

53,350 

23.5 

60.8 

if 

8.50 

34,800 

52,675 

26.0 

65.7 

1 ? 

9.75 

33,100 

52,400 

25.3 

63.3 

if 

8.175 

34,325 

54,175 

22.0 

63.4 

if 

9.50 

33,175 

52,000 

23.15 

63.6 

1 7 

IT 

9.75 

31,875 

50,325 

23 2 

63.8 

2 

10.50 

31,800 

49,725 

22.3 

63.9 


* See also similar results on steel in Chap. XXV. 




































































































132 


THE MATERIALS OF CONSTRUCTION. 


for different finished sizes, it is necessary to make these several sizes from 
the piles whose areas of cross-section bear a constant ratio to those of the 
finished sections. The following table gives average results of four series of 
tests on wrought iron on sizes from one inch to two inches in diameter. 

As showing that a uniform reduction in the rolls may be made to produce 
iron of equal strength for these same sizes, the following table of results is 
given, the iron having been rolled and the tests of strength made expressly 
to establish this fact.* 

TABLE X.—DIMENSIONS AND AREAS OF PILES, AREAS OF BARS IN 
PERCENTAGE OF AREAS OF PILES, TENSILE STRENGTH, ELASTIC 
LIMIT, ETC., OF NINE BARS. 


Size of Bar. 

Dimensions of 
Piles. 

Area of Piles. 

Area of Bars in 
Per Cent of 
Area of Piles. 

Tensile Strength. 

Elastic Limit. 

Inches. 

Inches. 

Sq.In. 

Per Cent. 

Pounds. 

Pounds. 

2 

8 X 10 

80 

3.92 

50,763 

33,258 

n 

8 X 10 

80 

3.45 

53,361 

35,032 

u 

8X9 

72 

3.34 

53,154 

35,323 

H 

8X8 

64 

3.24 

53,329 

33,520 

H 

6X9 

54 

3.27 

52,819 

34,840 

if 

•6X7 

42 

3.53 

52,733 

34,606 

li 

6X6 

86 

3.41 

53,248 

33,529 

H 

6X5 

30 

3.31 

54,648 

34,695 

l 

5X5 

25 

3.14 

53,915 

36,287 


* These two tables of results are compiled from data given in the report of the U. S. 
Board on Testing Iron and Steel, vol. i, 1881. 
















CHAPTER IX. 


STEEL. 

METHODS OF MANUFACTURE. 

96. The Crucible Process is the oldest and simplest of those used at the 
present time, and is still used for the finer grades of tool-steel. A pure 
grade of wrought iron is first rolled into flat bars and cut into convenient 
lengths. These are then heated for from three to six days in " cementing 
furnaces,” where they are tightly enclosed in boxes separated by layers of 
fine charcoal. This recarburizes the wrought iron at the rate of about -J- 
inch in depth every twenty-four hours, and makes cement or blister steel.* 
This was the steel of commerce until 1740, when it was first remelted in 
crucibles (by Daniel Huntsman, in England), thus making what is still 
known as crucible steel. These crucibles are now heated in a Siemens re¬ 
generative gas-furnace, similar to that described in Art. 98. Cheaper grades 
of crucible steel are made by remelting in crucibles Bessemer scrap. The 
cheaper Bessemer and open-hearth processes have now limited the use of 
the crucible process to the manufacture of high-grade tool and spring steel 
only. In 1896 the total annual capacity of crucible-steel furnaces in the 
United States was about 100,000 gross tons. 

97. The Bessemer Process. —This consists of a decarburization of crude 
pig iron by means of finely divided air-currents blown through the iron when 
in a melted state. The oxygen in the air burns out the silicon and carbon 
from the melted cast iron, and this combustion so raises the temperature of 
the melted mass that it remains a mobile fluid even after these foreign in¬ 
gredients have been almost wholly removed. This requires a very high 
temperature indeed, and one which could not be obtained in the ordinary 
puddling-furnace. The purified iron is the;i “recarburized” by adding 
melted spiegeleisen which contains from 10 to 20 per cent of manganese, 
and also some carbon and silicon. This manganese unites with the large 
amount of oxide of iron present, which was formed by the blast, and which 
would cause the product to be red-short and to crumble in working, and 


* Also called shear, double shear, or German steel. 


133 





134 


TEE MATERIALS OF CONSTRUCTION. 


at the same time the proportion of carbon is brought up to any desired 
amount. The whole mass is then poured off into ladles, and thence into 
cast-iron moulds. These masses of cast steel are now called ingots. This 
process was invented by Sir Henry Bessemer of England, and perfected by 
G* if. Goransson of Sweden,* in 1858. 

In this process the crude melted iron is tapped directly from the cupola, 
furnace, and in Sweden directly from the blast-furnace into the converter, 
which is a large steel vessel, mounted on trunnions, lined with refractory 
materials, with a removable bottom provided with many small openings 
or tuyeres. This vessel is turned down into a horizontal position to 
receive its charge. The blast is then started and the vessel raised 
to a vertical position, the air-pressure being sufficient to keep the 
melted iron from entering the air openings in the base. In Sweden, 
where a very pure iron is used, the blast is stopped when the appearance of 
the shower of sparks issuing from the mouth of the converter indicates the 



Fig. 62.—Chemical Reductions of an Open-hearth Converter, (Howe, Jour. Ir. & 

St. Inst., vol. n. p. 102.) 


desired percentage of carbon, when the metal is at once poured off into the 
moulds. As this criterion is a very uncertain one, it is customary in this 
country to continue the blast till practically all the carbon has been con¬ 
sumed, this stage being clearly indicated by the changed appearance of the 
flames. The addition now of manganese and carbon, in any desired pro¬ 
portions, is readily made. It is important to remember that by this process 
no sulphur or phosphorus is removed, and hence only pig irons compara¬ 
tively free from these elements can be used for the Bessemer process, such 
iron being known as Bessemer pig. The iron must contain from 1^ to 24 
per cent of silicon in order that by its combustion it may sufficiently heat 
the charge to keep it fluid when the carbon is consumed. If there is as 
much as 2\ per cent of silicon in the pig-iron, from 10 to 15 per cent of 


* See paper by Prof. Rich. Ackerman of Stockholm, in Trans. Am. Soc. Min . 
Engrs., vol. xxii. p. 266. 












STEEL. 


135 


cold steel scrap can also be worked into the charge without chilling it. 
The rate of burning the silicon, carbon, and manganese is shown in Fig. 62. 
The combustion of the silicon brings to the mass about nine times as much 
heat as the combustion of the same amount of carbon. One reason for this 
is that the pioducts ot the combustion of silicon form a slag which remains 



Fig. 63.—Plan and Sectional View of a Bessemer-steel Plant. 

in the converter, while the product of the combustion of carbon is a gas 
which passes off and carries much heat with it. 

In Figs. 63 to 67 are shown the characteristic features of a standard 
American Bessemer-steel plant. On the right of Fig 63, in plan, are 
shown four cupola-furnaces, with a blower, for melting the pig iron. The 
sectional view shows these to be placed at a high elevation, so that the 
melted iron, received in the ladles K f which stand on platform-scales for 
weighing the charge, can be poured into the spouts MN, and run directly 
into the mouth of the converter, which is then turned into the position 
shown in Fig. 65. The blast is now started through the base of the con¬ 
verter, and it is raised to a vertical position, Fig. 66, and the blast kept on 







































































































































































136 


THE MATERIALS OF CONSTRUCTION. 




o 


nf®oPvV 
:h|o 0 0 0 0 k; 

w §oM 

x? '!-•(- 





Fig, 64.—Views of the American Form of Bessemer Converter, showing the Movable 

Bottom. 


















































































































STEEL. 


137 



till first the silicon and then the carbon has been burned out. The con¬ 
verter is then again revolved to a hori¬ 
zontal position, and the blast stopped. 
The proper amount of melted spiegel- 
eisen which is kept melted in the two 
reverberatory furnaces RR is then run 
into the converter, whereupon it is at 
once poured into the ladle, which is 
operated by a crane which swings it in 


Fig. 66.—The Bessemer Converter 
Action. 


in 


Fig. 67.—The Valvular Ladle. 


the path of a circle over the several ingot-moulds, the metal falling 
through a valve at the bottom, as shown in Fig. 67. The motions of the 
converter and also of the crane, as well as the blast, are all controlled from 
one platform by levers operating hydraulic machinery. 

The Swedish practice of taking the iron directly from the blast-fur¬ 
nace is growing in this country, but it is here first run into a large vessel 
containing from 100 to 150 tons of melted iron, called a mixer, in order to 
obtain a more uniform product. This mixer also serves as a reservoir for 
equalizing the inequalities of supply from the blast-furnace and demand 
from the converter. From this mixer it is drawn into ladles on cars, and 
run to an elevated platform and poured into the converter. This is called 
the direct process. It may be employed when the blast-furnaces are re¬ 
moved from the Bessemer plant as far as one or two miles. 

Recently a means of removing phosphorus has been found in the addi¬ 
tion of calcined lime to the charge in the converter.* The phosphorus 
unites with the lime and so passes into the slag. In this case the lining of 
the converter must also be “ basic ” to keep the slag from uniting with it 
and so rapidly consuming it, so the lining is then made of a calcined mag¬ 
nesian limestone (dolomite) and tar, made into brick, or rammed into place. 
This is called the basic Bessemer process, but its use had been abandoned 
in America because of some unfortunate failures when first introduced. 


* By S. G. Thomas and P. C. Gilchrist, England, 1878. 

















































































138 


THE MATERIALS OF CONSTRUCTION. 


The method has now (1896) been revived at Troy, N. Y., with marked 
success. 

The Bessemer is the cheapest known process of making steel. This 
process alone has revolutionized many lines of industry, and has led to the 
replacing of wrought iron by steel in all the more important uses of these 
materials. The Bessemer process is now used exclusively for making steel 
rails for steam and electric roads, and for all the cheaper grades of steel 
plates and structural forms. For the better grades of structural material it 
is being replaced by— 

98. The Open-hearth Process.—In this process pig iron, cast iron, and 
wrought-iron and steel scrap are converted into steel under the direct 
action of an oxidizing flame in a regenerative gas-furnace. It was patented 
in 1845 by Heath, but was not found to be successful until Siemens had 
developed his regenerative gas-furnace about 1862. Since about 1870 



Fig. 68. —Transverse Section of a Typical Open-heartli Regenerative Gas-furnace. 


these furnaces have multiplied rapidly, and in 1896 the total capacity of 
these furnaces in the United States was 2,400,000 gross tons, as against a 
total capacity of 9,400,000 gross tons by the Bessemer process. 

The more common type of furnace used for this purpose is shown in 
Figs. 68 and 69. The fuel used is what is known as producer-gas. This 
is a mixture of carbon monoxide and hydrocarbons, diluted with about 60 per 
cent of nitrogen. It is formed in gas producers in which coal is burned in 
air-tight ovens with an insufficient supply of air, this supply being fed in 










































































































































STEEL. 


139 


under piessure and in known volumes. This producer-gas is brought to 
the hearth area of the open-hearth furnace through a passageway entirely 
filled with red-hot fire-brick stacked to form an open checker-work, as 
shown at E and F in Figs. 68 and 69. 



Fig. 69.—Longitudinal Section of a Typical Open-lieartli Regenerative Gas-furnace. 

As this hot gas enters the furnace area it is mixed with streams of hot 
air which has also been drawn in over red-hot brick surfaces, and the com¬ 
mingling of these red-hot gases, in proper proportions to produce complete 
combustion, develops the most intense heat possible to obtain by the com¬ 
bustion of gases. In the reverberatory furnace, where the flame of an 
ordinary coal fire is employed, the maximum temperature attainable is 
about 3,500 degrees F., but in the Siemens regenerative gas-furnace a tem¬ 
perature of 4500 degrees F. may be maintained. The regenerative princi¬ 
ple consists in the utilization of the heat of the escaping gases in reheating 
the fire-brick placed in the air and gas passageways. To do this it is of 
course necessary to alternate the incoming and the escaping gases in two 
sets of passages, this being done by simply moving certain valves every 
twenty or thirty minutes. 

In Fig. 68 K is the furnace hearth; EE are air-chambers and FF gas- 
chambers, the checker brickwork being shown in one only of each, but it 
really fills all four of these passageways. The red-hot gas enters the 
furnace through the lower ports IT, Fig. 68, and BB, Fig. 69; while the air 
enters just above these through an annular space I, Fig. 68, and C, Fig. 
69. The furnace itself, therefore, is like a great argand gas-burner in its 
method of receiving and burning the gas. The depressed roof of the fur¬ 
nace throws the heat strongly upon the materials placed on the hearth. 









































































































































































140 


TEE MATERIALS OF CONSTRUCTION. 


while the gases themselves are forced to play upon the melting metal. The 
flame has an excess of oxygen so that it is an oxidizing flame, and would 
rapidly waste unmelted wrought-iron or steel scrap placed in it. It is cus¬ 
tomary, therefore, to place first on the hearth pig or cast iron on which the 
oxidizing flame acts by consuming first the silicon and then the carbon, at. 
the same time oxidizing some iron which by melting forms a slag which 
floats on the bath of melted metal. After such a bath has been prepared 
the wrought-iron and steel scrap can be thrown in, since these will now be 
covered by the bath and so protected from the oxidizing flame. The 
facilitv with which such scrap can be remelted and made over into new 
ingots by this method is one of its chief elements of value. If one could 
always choose his ingredients at pleasure he could so proportion them that 
little or no decarburization would be necessary, a simple melting together 
giving the requisite proportions. 

The final removal of any excess of carbon, after the products have melted, 
is effected by means of the melted oxide of iron, which floats on the surface 
at first, but which afterwards becomes thoroughly mixed with the mass by 
the boiling action of the escaping gases when the temperature becomes high. 
Some of the oxygen of this iron oxide combines with the carbon of the 
melted iron and comes to the surface as carbonic oxide, where it is burned to 
dioxide and passes out with the other consumed gases. This also restores 
a corresponding portion of the iron of the oxide slag to the metal bath and 
so adds to the product. 

When a large amount of pig or cast iron is to be reduced, it is common 
to charge a suitable amount of oxide of iron ore to supply the requisite 
amount of oxygen to decarbonize the cast iron, and so to hasten the process 
and also to avoid the necessity of creating so much artificial oxide of iron by 
the oxidizing flame. The remaining portion of the oxide slag not destroyed 
by giving up its oxygen to the carbon in the bath is neutralized and chemi¬ 
cally destroyed by adding a charge of spiegeleisen containing 20 or 30 per 
cent of manganese, or an artificial ferromanganese containing some 80 per 
cent of manganese, just before pouring. The manganese unites with the 
oxygen of the slag, and restores the iron to the bath the same as is done in 
the Bessemer process. There, however, it was usually desired to add carbon 
also, and hence this process has come to be known as recarburization , or the 
adding of a recarburizer. In the open-hearth process the carbon is not all 
burned out, as it is in the Bessemer process, but by taking samples out with 
a small dipper or ladle, and casting these, cooling them in water, and break¬ 
ing them, the operator can tell when he has the carbon ingredient brought 
to the desired amount. He seldom wants to add carbon, therefore, in the 
open-hearth process, but must add the manganese to destroy the oxide slag 
which, if poured off with the iron, would make it red-short, or unmalleable 
in the rolls. The manganese charge should more properly be called a 
“ deoxidizer,” but, by analogy from the Bessemer process, the same term of 
“ recarburizer ” is applied here to this manganese charge. 


STEEL. 


141 


The pervasive action of this manganese charge in the open-hearth furnace 
is very remarkable. The manganese has so strong an affinity for the oxygen 
in the iron oxide that it seems quickly to seek it out throughout all parts of 
the bath, and even when added to the metal in the ladle, after teeming, 
it seems to be equally effective. In the case of the Bessemer process, how¬ 
ever, it is necessary not only to destroy the iron oxide, but to add a carbon 
ingredient to the metal. To secure a uniform distribution of this carbon 
element through the mass seems to require a thorough artificial mixing. 
The only action of this kind which is secured in the Bessemer process is had 
in the pouring off into the ladle and the drawing from the pouring-nozzle in 
its bottom into the ingot-moulds. This does not insure a uniform distribu¬ 
tion of the carbon, and hence it is not very uncommon to find great differ¬ 
ences in the mechanical qualities of different portions of the same sheet of 
Bessemer steel. In the open-hearth process little or no carbon is added in 
the “ recarburizer,” so that the mixture retains the homogeneity it neces¬ 
sarily secures from the violent boiling action of the hath. This greater 
homogeneity and reliability, when judged by sample tests, has led to a 
general preference for open-hearth steel by engineers in all kinds of struc¬ 
tural designing. 

Here, as in the Bessemer process, there is no elimination of the phos¬ 
phorus and of the sulphur. This has greatly limited the range of materials 
which could be fed to this furnace, and it has led here, as in the case of the 
Bessemer process, to the use of a charge of calcined lime to unite with the excess 
of phosphorus* and hold it in the slag, which is then drawn off. But, as with 
the Bessemer furnace, this lime would unite with the sand lining of the 
furnace to form a flux which would quickly destroy this lining altogether. 
To prevent this, those furnaces in which lime is to be added to the charge 
are themselves lined with calcined dolomite limestone, and these are called 
basic-lined furnaces, and this process has thus come to be known as the basic 
open-lieartli process. It must be understood, however, that neither here nor 
in the Bessemer process does the lining play any part in the process itself. 
The process, in each case, depends on the materials charged and not on the 
furnace lining. The lining is simply made such as will not be attacked by 
the slag formed, and is always intended to be neutral, or inert. In 1890 
about one half of the open-hearth steel made in the United States was by 
the basic process. 

To distinguish the ordinary open-hearth process, in which a sand or 
silica lining is used and no lime fed in the charge, that is to say, in which 
no attempt is made to remove any of the phosphorus in the ingredients used, 
from this “ basic ” process, the former is now called the acid open-hearth 
process. It was formerly known as the Siemens-Martin process, from its use 
of the Siemens furnace and from the fact that the Messrs. Martin of France 


* When steel is very low in carbon some phosphorus, as 0.03 or 0.04 per cent, seems 
desirable to add strength to the metal. 




142 


THE MATERIALS OF CONSTRUCTION. 


first employed the open-hearth in this way, but without the Siemens regen¬ 
erative gas-furnace. 

99. Comparison of the Basic and Acid Open-hearth Processes. —From 

what has been given in the previous article it is evident that poor steel and 
steel high m phosphorus may be made by either process, due to ignorance, 
carelessness, or inexperience. By the use of the basic process ingredients 
high in phosphorus may be employed, and thus the available materials are 
very much increased and hence cheaper grades can be employed. The 
process itself is somewhat more expensive than the acid process. When the 
acid process is used, unless there is a rigid inspection and control over the 
product, there is a danger that the cheaper (phosphorus) ingredients may be 
used, and so lead to a brittle product, whereas if the basic process be speci¬ 
fied and employed the cheaper ingredients are anticipated, and the removal 
of the phosphorus provided for. The maker can be trusted to reduce the 
sulphur in order to make the product malleable when hot, so as to roll 
smoothly, as defects here are patent to any one. Engineers now generally 
specify the open-hearth process without prescribing the kind of lining, but 
naming a maximum proportion of phosphorus. This upper limit of phos¬ 
phorus is now commonly taken at from 0.0G to 0.08 per cent, but Mr. II. II. 
Campbell,* who is the highest authority from the standpoint of the manu¬ 
facturer, says this upper limit should now be made 0.04 }:)er cent. If this 
phosphorus limit is not specified, or if specified but not determined by actual 
tests, then it would be safer to specify the basic open-hearth method, f 

100. Comparison of Bessemer and Open-hearth Steel. —Comparing the 
products only (not the processes) of these two general methods of making 
steel on a large scale, we may say: 

1. While for like chemical analyses like mechanical properties may be 
anticipated from these two methods, yet all the unexplained accidental failures 
of steel have occurred on Bessemer steel. Engineers have become suspicious 
of it. Open-hearth steel is therefore more reliable than Bessemer steel. 

2. Test specimens cut from different parts of the same Bessemer steel 
plates have shown extraordinary differences in their mechanical properties. 
This has never been found in open-hearth plates. They are therefore more 
homogeneous than Bessemer plates. 

3. Bessemer steel products found on the general market are apt to be 
extremely irregular in their composition, though rolled into like forms and 
sold to serve the same purposes. Open-hearth products purchased in the open 
market and designed to serve the same purposes are more uniform in quality. 

4. The open-hearth steel may be tested before tapping off, and its com¬ 
position adjusted at pleasure, and this is usually done. Bessemer steel 

* Superintendent Pennsylvania Steel Co., Steelton, Pa. 

f In January, 1896, there were in operation in the United States open-hearth-steel 
plants having an annual capacity of 2,430,000 gross tons, 700,000 of which capacity had 
been added in the preceding two years, more than one half of them using the “ basic ” 
process. Thirteen of these new furnaces are to be used in making steel castings. See 
R R- Gazette , Sep. 3, 1897, for description of the Ill. Steel Co.’s plant, with tilting fur¬ 
naces. 




STEEL . 


143 


TABLE XI.—TESTS SHOWING THE HOMOGENEITY OF OPEN-HEARTH METAL.* 


Heat 10,699. Acid Open-hearth. 
Test-bars, f " rolled rounds. 


Elastic Limit, 
Lbs. per Sq. In. 

Ultimate 
Strength, 
Lbs. per 
Sq. In. 

Elongation 
in 8 In., 
Per Cent. 

Reduction 
of Area, 
Per Cent. 

Elastic Limit, 
Lbs. per Sq. In. 

Ultimate 
Strength, 
Lbs. per 
Sq. In. 

Elongation 
in 8 In., 
Per Cent. 

Reduction 
of Area, 
Per Cent. 

35,900 

53,510 

28.75 

64.14 

31,140 

52,760 

32.75 

60.60 

36,450 

54,790 

31.75 

64.58 

31,790 

52,750 

32.75 

61.20 

36,000 

56,150 

28.75 

62.71 

31,540 

53,000 

31.50 

56.50 

36,225 

55,690 

31.25 

64.48 

31,250 

52,000 

32.25 

63.30 

36,090 

55,830 

31.00 

64.71 

31,250 

52,320 

34 00 

64.10 

36,315 

55,830 

32.00 

65.18 

31,080 

52,320 

32.50 

57.10 

36.740 

56,370 

31.50 

64.84 

31,160 

52,830 

32.75 

61.80 

36.350 

55,090 

29.50 

62.87 

31,250 

53,160 

32.75 

58.10 

36,450 

57,510 

31.25 

64.25 

31,040 

52,160 

32.75 

61.80 

36,125 

56,900 

30.75 

64.26 

32,050 

53,840 

32.50 

59.60 

37,580 

56,600 

33.50 

64.16 

31,660 

53,580 

32.50 

61.10 

36,900 

57,510 

30.50 

65.16 

31,700 

52,480 

32.25 

53.10 

37,220 

57,420 

31.25 

63.28 

32,550 

52,580 

34.00 

63.10 

37,130 

57,280 

31.75 

64.16 

32,570 

52,960 

32.75 

65.40 

36,000 

57,050 

31.25 

65.75 

33,330 

53,050 

33.00 

60.40 

35.860 

57,190 

31.25 

64.23 

33,580 

53,860 

33.00 

60.40 

36 615 

57,440 

57,670 

57,580 

57,350 

31.25 

64.74 



36,450 

31.75 

66.46 





37,165 

36,640 

32.75 

63.68 





31.25 

63.18 









Av. 36,510 

56,538 

31.15 

, 

64.34 

Av. 31,809 

52,853 

32.75 

60.48 

t 

Heat 11,018. Acid Open-hearth. 

Heat 1,820. Basic Open-hearth. 

Test-bars, f" rolled rounds. 

Test-bars, |' rolled rounds. 

Elastic Limit, 
Lbs. per Sq. In. 

Ultimate 
Strength, 
Lbs. per 
Sq. In. 

Elongation 
in 8 In., 
Per Cent. 

Reduction 
of Area, 
Per Cent. 

Elastic Limit, 
Lbs. per Sq. In. 

Ultimate 
Strength, 
Lbs. per 
Sq. In 

Elongation 
in 8 In., 
Per Cent. 

Reduction 
of Area, 
Per Cent. 

36,700 

58,400 

28.00 

66.20 

33,065 

48.340 

34.50 

71.87 

37,150 

57,840 

. 30.75 

65.60 

31,530 

47,380 

35.00 

72.05 

37.280 

56,880 

29.50 

58.60 

33,650 

48,450 

35.00 

72.05 

36,060 

56,940 

28.50 

53.30 

31,600 

48,230 

37.00 

74.14 

36,420 

56,700 

30.75 

63.10 

33,340 

49,175 

36.25 

70.09 

36,060 

57,180 

30.25 

65.50 

32,760 

48,560 

33.75 

79.25 

35,780 

56,800 

31.00 

65.40 

33,260 

47,730 

35.00 

74.49 

36,700 

57,440 

30.00 

63.80 

32,130 

48,785 

34.00 

71.80 

35,780 

56,800 

31.00 

65.40 

32,935 

48,640 

34.25 

71.92 

36,700 

57,440 

30.00 

63.80 

33,270 

49,440 

34.00 

71.48 

35,700 

56,900 

32.50 

67.10 

32,900 

- 47,835 

34.00 

72.72 

37,020 

57,180 

31.25 

59.70 

31,920 

48,050 

33.75 

71.42 

37,400 

57,320 

30.50 

68.10 

32,185 

48,360 

36.25 

74.28 

37,260 

56,780 

30.25 

67.20 

33,880 

48,400 

33.75 

73.64 

37,480 

57,420 

31.00 

66.30 


• • • • • 

• • • • 

• • • • 

Av. 36,634 1 

I 

57,201 * 

30.25 

i 

63.94 

Av. 32,745 

48,384 

34.75 | 

72.49 


Heat 10,910. Acid Open-hearth. 
Test-bars, 1£" rolled rounds. 


* Specimens coming from final forms which were rolled from the upper part of the 
original ingot have uniformly a higher tensile strength and elastic limit and a lower per¬ 
centage of elongation than specimens coming from the bottom of the ingot. See Eng. 
News, Mar. 31, 1898. 






















































































144 


THE MATERIALS OF CONSTRUCTION. 


usually goes as blown, without correction. The open-hearth product is 
therefore under better control. 

5. The remarkable homogeneity of open-hearth steel is indicated by the 
preceding series of tests (Table XI) on specimens cut from different por¬ 
tions of plates rolled from four different heats.* 

101. Molecular Structure of Wrought Iron and Steel. —One of the most 
important facts for the engineer to fix in his mind is this: All grades of iron 
and steel , originally formed in a molten state, will always thereafter, when 
cooled after either a melting, forging, or rolling, take a crystalline form. 
That is to say, all cast, or ingot, metal is always crystalline whether cast, 
hammered, or rolled to its final forms. f This includes all the grades of 
“ steel ” as given in the second classification, p. 89, as well as the cast iron 
and cast steel. 

It may also be said that tor ought iron also shows a crystalline structure 
whenever a portion of the iron in the puddle-ball was in a liquid condition 
when removed from the furnace. This liquid iron may result either from 
the entangling of unreduced but melted cast iron in the glutinous mass, or 
from too high a temperature of the furnace, resulting in the melting down 
(burning) of the reduced metal, or wrought iron proper, which when 
“ brought to nature” and at the proper temperature should be a spongy, 
pasty mass, sufficiently firm to be handled with the puddling-bars. This is 
only a special case of ingot metal, since so much of the iron in the puddle- 
ball as comes out in a liquid form is, within itself, free from the slag which 
covers the more pasty iron mass, within and without, as a slime might 
adhere to the entire internal and external surface of a sponge which has been 
lifted from it and squeezed. Any given portion of this puddle-ball, when 
finally rolled out into plates and bars, will become a small filament or fibre 
of the cross-section, but greatly extended in the direction of the rolling. 
Thus, if a small pocket of liquid iron was entangled in the ball, this would 
become a small crystalline thread throughout the bar. A larger mass of 
melted metal would make a longer crystalline portion of the cross-section. 

When wrought iron is properly made, that is, when it is entirely reduced 
or “ brought to nature,” and when the furnace is not so hot as to melt the 
pasty mass, wrought iron will be found to be practically free from crystalline 
formations, and to be wholly fibrous. The fibrous structure is due to the 
continuous mixture of the slag with the iron, which, after repeated piling and 
rolling, leaves the slag so distributed through the mass in thin filaments as 
to prevent any visible crystalline arrangement of the molecules, although 
each such filament is really a series of distorted (usually elongated) crystalline 
forms. 


* From H. H. Campbell’s paper on “ The Open-hearth Process ” before the World’s 
Engineering Congress. Trans. Am. Inst. Min. Engrs., vol. xxii. p. 352. 

f That is to say, when shaped while hot. When shaped cold, as by cold rolling or 
wire-drawing, the crystalline form may be partly or even wholly destroyed. 




STEEL. 


145 


102. Fracture Showing Structure.—In order to obtain a normal fracture 
of any malleable metal, or one which shows the true character of the molec¬ 
ular arrangement, uninfluenced by the distorting effects of the forces used 
to produce the fracture, it is common to nick the specimen with a chisel and 
bend it.* This, however, subjects one side of the uncut section to a cotn- 
pression, and the other to a tension; and even if a fracture is effected, the 
entire surface has not been treated alike. It is better, therefore, to turn a 
sharp groove into the side of the specimen all around (or nick it with a 
chisel), and then to pull the specimen in two in a testing-machine. This 
will always reveal the true structure of the metal, without the distorting 
effects accompanying the cold drawing out (elongation) of the specimen which 
is purposely sought in the ordinary tensile test. To insure against any 
elongation whatever, the tool used must be perfectly sharp at the point, so 
that the bottom of the groove is a true angle, and not a curve with a finite 
radius. When good structural steel is tested in tension it elongates at the 
ruptured section fully 100 per cent; that is, it stretches here to more than 
twice its original length, and this cold drawing out of the metal wholly 
destroys its original molecular arrangement, so that the fracture always look 
“ fibrous ” or “ silky.” This universal aj:>pearance of soft and medium steel 
when pulled in two leads many persons to suppose that this material has not 
normally a crystalline arrangement. When, therefore, they find this same 
material broken in use, as on a screw-thread, or at a shoulder, or at a sudden 
reduction of section, and they discover it having a wholly crystalline struc¬ 
ture, they conclude that this is abnormal, and that the material has 
<£ crystallized in service.” The simple test described above, of pulling a 
grooved specimen, will prove that all grades of steel, even to the softest ingot 
iron, has normally a crystalline structure. If the nicking test be cited to 
prove this fact, it is often claimed that the nicking produced such a jarring 
of the metal as to cause it to instantly rearrange its molecules, while cold and 
rigid, into the crystalline form! Surely the grooving in a lathe is not open 
to even this shadowy ground of suspicion. 

If wrought iron be grooved and pulled as here described, it will be found 
to be apparently wholly fibrous (if of a superior quality, the crystallized 
filaments being so small), or containing occasional small crystalline patches, 
(if of an ordinary quality), or sometimes nearly wholly and coarsely crystal¬ 
line (if of a very inferior quality). It is therefore said to be normally of a 
fibrous or non-crystalline structure. Now when wrought iron breaks in 
service and reveals a coarsely crystalline structure, it simply indicates, in 
the opinion of the author, the original poor quality of the material, and does 
not prove that the material had crystallized in service as is geuerally sup- 


* Metcalf affirms that a skilful workman can grade steel, by the fracture, for cus¬ 
tomers, so closely that “year after year not one piece will vary in carbou more than 
0.05 per cent above or below the mean for that temper.” Steel, p. 6. This can only be 
true of material from the same establishment produced under like conditions. 




146 


THE MATERIALS OF CONSTRUCTION. 


posed. This subject has been discussed at considerable length in Article 
93. 

103. Structure of Steel as Affected by Heat Treatment.—While steel or 
ingot iron is entirely free from slag and similar foreign ingredients, it must 
not be regarded as a simple or single mineral, or substance, but rather as a 
substance, like granite, made up of a number * of separate minerals or 
“ metarals ” (a term suggested by Ilowe), each crystallizing out by itself, 
or being left as a matrix after the more controlling minerals have crystallized 
out. The particular final arrangement depends on which of these various 
proximate combinations control in the crystallizing stage of cooling, and also 
on the heat treatment it receives. Concerning the effect of the heat treat¬ 
ment on the appearance of the fracture, the following statements are based 
on the discussion of this subject by Howe (§§ 240-250). (See also Appen¬ 
dix A.) 

1st. There is a critical temperature, at a “ low yellow ” heat (lower for 
high-carbon and higher for low-carbon steel), above which the material 
forms rapidly into coarse crystals. 

2d. If cooled either slowly or rapidly from above this temperature, it is 
coarsely crystalline, the coarseness of the crystals depending on the time 
allowance for their formation when at this higher temperature. 

3d. If worked (forged or rolled) in cooling from this higher temperature, 
the crystallization is that characterizing its temperature when leaving the 
hammer or rolls. 

4th. If raised from a temperature below a low red, just to this critical 
temperature, whatever its previous condition, or if worked down to this 
critical temperature in cooling from a higher, and cooled rapidly as by 
quenching in water or oil, it is so finely crystalline as to appear amorphous, 
or porcelanic, to the naked eye. If cooled slowly from this critical tempera¬ 
ture, it is finely crystalline to the naked eye. 

5th. Since there is no tendency to crystallize below a low red heat, it is 
sufficient to cool rapidly from the critical temperature (low yellow) down to 
a low red, or to continue to work the metal to this temperature, after which 
the cooling may be slow, thus preserving the porcelanic fracture and obtain¬ 
ing a greater toughness. 

6th. As an illustration of the effects of these different treatments, we 


have f 

For slow cooling after forging, size of grain. 0.1414 in. diarm 

Reheated to the low yellow and cooled slowly, size of grain 0.0048 “ 

Reheated to low yellow, quenched in water to low red, and 

then slowly cooled, size of grain. 0.0004 “ 


- Seven such having already been distinguished; see Howe’s Metallurgy of Steel, % 237. 
Osmond has recently added at least two new ones, and furthermore diamond has now 
been isolated from certain steels. Stahl u. Eisen, vol. xvi, No. 15, 189G. 
f Quoted by Howe, § 250, from Chernoff. 






STEEL. 


147 


The size of this last is entirely too small to be discoverable by the naked 
eye, and hence it would appear amorphous or porcelanic. 

7th. The bright surfaces observed on a steel fracture may be either 
cleavage planes across individual crystals, or their exterior sides, depending 
on which surface offers the least resistance to rupture. In either case the 
size of these individual surfaces is a true index of the coarseness or fineness 
of the crystalline structure. 

8th. The appearance of a steel fracture is thus a good indication of the 
condition of the metal when it left the rolls, or of its subsequent treatment. 
The student should himself verify these statements at the forge. 

This subject will be discussed again when treating of hardening, temper¬ 
ing, and annealing. See Arts. 130 to 134. 

104. The Mechanical Qualities of Steel.—When the term steel is made 
to include all grades of ingot metal as well as converted wrought iron, its 
qualities are so various as to necessitate a series of trade names, such as 
flange-steel and shell-steel, for boiler-plates; tank-steel, for plates of uncer¬ 
tain quality and of cheap manufacture, often used where a better grade is 
needed; structural steel, both mild and medium, used for all kinds of 
structural shapes, as angles, I beams, channels, T’s, etc.; rail-steel, used 
for railway rails, both steam and electric; machinery-steel, especially adapted 
to forging and welding; tool-steel, spring-steel, saw-steel, etc. 

The special qualities required of these various grades of steel are approxi¬ 
mately as follows: 

Fire-box Steel , Flange-steel, and Rivet-steel —used for locomotive fire¬ 
boxes, boiler-heads, rivets, and other purposes where it is subject to great 
deformations in service, or where it must be shaped, or dished, in manufac¬ 
ture in such a way as is only practicable with a very soft, or pliable, semi-plastic 
material. This grade of steel, therefore, must be ductile rather than strong, 
and extremely tough and capable of resisting great abuse, either cold or hot, 
without losing its strength or toughness. This steel has a tensile strength 
of from 50,000 to 00,000 lbs. per square inch; an elastic limit* of from 
30,000 to 40,000 lbs. per square inch; an elongation of from 25 to 35 per 
cent in eight inches; a reduction of area of from 50 to 65 per cent at the 
fractured section. It will also bend cold through 180, and close down per¬ 
fectly flat, as in Fig. 71, either under the hammer or in a press, up to a thick¬ 
ness of | inch to 1 inch without showing any sign of fracture. One could 
literally tie it in knots while cold, as in Fig. 70 without sign of rupture. 
Made now mostly by the open-hearth process. 

Shell-steel is used for boiler-shells, and for structural purposes, where a 
greater tensile strength may be obtained at the expense of some ductility. 
This steel has a tensile strength of from 55,000 to 65,000 lbs. per square 
inch; an elastic limit of from 33,000 to 44,000 lbs. per square inch; an 
elongation of from 25 to 30 per cent in eight inches; a reduction of area of 


* Here the commercial elastic limit is meant, or the break-down point. 



148 


TUE MATERIALS OF CONSTRUCTION. 


from 50 to GO per cent at the fractured section. Made by the open-hearth 
and the Bessemer processes. 



Fig. 70. —Knot of Rivet-steel, f in. in diameter, pulled to Incipient Fracture by the 

Author. 



Fig. 71.—Flange-steel Plates, f in. thick. 

Tank-steel has no particular limits of quality. It is a term which means 
the cheapest grade of steel plate on the market; is sold with no guarantee: 
its qualities usually unknown, or at least unrevealed; is likely to be extremely 





STEEL. 


149 


various in quality, even in different parts of the same plate; and should be 
used only for indifferent purposes. Made by the Bessemer process. 

Structural Steel is used for bridges, roofs, steel skeletons of buildings, 
etc., and should be of a superior quality. Several grades are recognized, 
although these names are used loosely, and have no precise meaning. Thus 
soft and mild structural steel may be regarded as the same in quality as the 
flange and shell steel respectively described above. Medium structural steel 
might be considered as having a tensile strength of from 60,000 to 70,000 
lbs. per square inch; an elastic limit of from 35,000 to 45,000 lbs. per square 
inch; an elongation of from 20 to 25 per cent in eight inches; a reduction 
of area of from 50 to 60 per cent at the fractured section. Hard structural 
steel having a tensile strength of from 65,000 to 75,000 lbs. per square inch 
is now used but little, as it suffers too much from shearing, punching, and 
assembling to make it as reliable as is desired for such material. Made by 
both the open-hearth and the Bessemer processes. 

Bail-steel must be very hard, with a high elastic limit to resist abrasion 
and wear, while it must also have great strength and resilience, or resistance 
to shock. It is a hard steel, having a tensile strength of from 70,000 to 
80,000 lbs. per square inch; an elastic limit of from 40,000 to 50,000 lbs. 
per square inch; an elongation of from 15 to 20 per cent in eight inches; a 
reduction of area of from 40 to 50 per cent at the fractured section. Made 
by the Bessemer process. 

Ordinary Tool-steel , Spring-steel , etc., are harder grades, capable of being 
hardened and tempered, in which the tensile strength and ductility are of 
less importance than its hardening qualities. The tensile strength here may 
be from 90,000 to 160,000 lbs. per square inch and the elongation very small, 
depending on the particular temper given to the specimen. Made by the 
Bessemer, open-hearth, and crucible processes. 

The Finer Grades of Tool- and Spring-steel, especially such as are to be 
used for edge-tools, are still made of crucible-steel. Metcalf gives the follow¬ 
ing tempers for their respective uses: 

“ 0.50 to 0.70 C for hot work and for battering-tools, and for tools of 
dull edge. 

“ 0.70 to 0.80 C for battering-tools, cold-sets, and some forms of reamers 
and taps. 

“ 0.80 to 0.90 C for cold-sets, hand-chisels, drills taps, reamers, and 

dies 

“0.90 to 1.00 C for chisels, drills, dies axes, knives, and many similar 
purposes. 

“1.00 to 1.10 C for axes, hatchets, knives, large lathe-tools, and many 
kinds of dies and drills if care be used in tempering them. 

“1.10 to 1.50 for lathe-tools, graving-tools, scribers, scrapers, small 
drills, and many similar purposes. 

“ The best all-around tool-steel is found between 0.90 and 1.10 C. This 
can be adapted safely and successfully to more uses than any other temper/' 


150 


THE MATERIALS OF CONSTRUCTION. 


This is at and just above the point of complete saturation of combined 
carbon. 

105. dualities of Steel as Affected by its Chemical Composition.—Mr. 

H. M. Howe, the highest authority on this subject, says (g 1): “I conceive 
steel to consist (A) of a matrix of iron which is sometimes (as in ingot iron 
and annealed steel), comparatively, or even quite pure, and sometimes (as in 
hardened steel, manganese-steel, etc.), chemically combined with a portion, 
or even the whole of the other elements which are present, probably in 
indefinite ratios, its mechanical properties being greatly affected by them; 
and (B) of a number of independent entities which we may style ‘ minerals,’ * 
chemical compounds of the elements present, including iron, which crystal¬ 
lize within the matrix, and by their mechanical properties, shape, size, and 
mode of distribution also profoundly affect the mechanical properties of the 
composite mass, though probably less profoundly than do changes of corre¬ 
sponding magnitude in the composition of the matrix.” 

And again (§ 237), “ From the microscopic study of polished sections 
iron (and steel) appears to be constituted, like granite and similar compound 
crystalline rocks, of grains of several distinct crystalline minerals, of which 
seven common ones have already been recognized, through peculiarities of 
crystalline form and habit, color, lustre, hardness, and behavior towards 
solvents. Their nature, size, shape, and orientation, and through these the 
structure and physical properties of the metal as a whole, seem to depend 
chiefly— 

1. On the ultimate chemical composition of the mass; 

2. On the mechanical treatment which it has undergone; 

3. On the conditions under which it has been heated and cooled, i.e., 
its “ heat-treatment,” which may induce the ultimate components of the 
mass to regroup themselves in new combinations, thus causing one set of 
minerals to give place to another.” 

When the iron or steel is in a state of fusion the ingredients are in mutual 
solution, and they do not separate until the fluid mass congeals or hardens, 
when one or another of these mineral ingredients crystallizes out first, and 
thus gives its own characteristics greater prominence than the other minerals 
which form the matrix, or which form in crystals later, and subject to the 
limitations as to form and size imposed by the previously formed crystals. 

Just as the character of a granite rock, therefore, is to be judged from 
the character of its mineral constituents, as proximate chemical compounds, 
and very imperfectly from ever so exact a determination of its ultimate ele¬ 
ments, so we must learn to rely with less assurance on the ultimate chemical 
analysis of iron and steel, and more on the proximate chemical compounds 
formed therefrom. Unfortunately these latter are very difficult of deter¬ 
mination, or even of identification, and hence we know very little about 
them. It is for this reason that we are as yet unable to infer with any great 


* But for which Mr. Howe suggests the term “metarals.” 




STEEL. 


151 


assurance the mechanical properties from the chemical analysis. Such con¬ 
clusions as may be drawn from chemical composition are partially summarized 
in the following articles. 

INFLUENCE OF CARBON ON IRON. 

106. Combination of Carbon with Iron.'—The effects of carbon on iron 
aie more pronounced and useful than those of any other known chemical 
element. Iron absorbs carbon readily, becoming saturated with about 4.6 
per cent of it, unless aided by manganese, when it may absorb as much as 
7 per cent. 

Cast Iron may be regarded as supersaturated with carbon, or as having 
some 4 per cent of this element in some form. 

11 rought Iron is nearly free from carbon in any form, having perhaps not 
over 0.10 per cent. 

Steel (ingot metal) may have anywhere from 0.05 to 1.50 per cent 
of carbon, the upper limit usually being about one per cent. For extreme 
hardness, steel may be made with as much as two or even three per cent 
carbon, while 0.9 per cent C gives maximum working qualities for tool¬ 
ed spring-steels. (This is the point of perfect saturation of combined 
carbon.) 

Three States of Cartoon in Iron. —Carbon is found in iron in three rad¬ 
ically different states: 

1. Mechanically mixed, in the form of <\> graphite, this being thrown out, 
or excluded, when cast iron crystallizes from a melted state. 

2. Chemically combined in unknown proportions, this forming a verv 
hard and strong compound, and the carbon so combined being here called 
hardening cartoon* 

3. Chemically combined, as a carbide of iron (Fe 3 C), up to the satura¬ 
tion-point of 0.9 C. It is intensely hard according to Sorby, though it 
does not appear to contribute to the hardness of steel to the same degree as 
the hardening carbon, f 

We shall therefore speak of the uncombined carbon as graphite (often 
called graphitic carbon), and the chemically combined carbon as hardening 
carbon and cement carbon . 

When the metal is fused all the carbon may be regarded as chemically 
■combined in the form of hardening carbon. When there is a great deal of 
this, as in cast iron, a large proportion of it is thrown out as graphite in the 
early stages of cooling, if sufficient time be allowed for this action to complete 


* Prof J. O. Arnold (Sheffield) gives the formula Fe 24 C for this component. Trans. 
Inst. Civ. Eng., vol. cxxm, 181)6. Many authorities agree with Osmond in attributing 
the hardness of quenched steel to an allotropic form of iron. Both sides are well 
presented in the discussion of Arnold’s paper, here cited. See Appendix A. 

f Besides these diamond has recently been isolated, and Ledebur adds “temper- 
carbon.” 



152 


THE MATERIALS OF CONSTRUCTION . 


itself. When there is not over 0.9 per cent of total carbon, none of it will 
appear as graphite in the cold product. 

A change from hardening carbon to cement carbon occurs (time permit¬ 
ting) at a low yellow heat, and no further change occurs below a low red 
heat. 

These changes and also the subsequent condition of the metal are indi¬ 
cated graphically, in a general way, in Figs. 72 and 72 a. Thus in Fig. 72 
the total carbon in cast iron being about 4 per cent, as soon as it begins to 



k M 0 A/ WE 

/OOOE TPAyf p /r c> 10 _ /] T / / O? F 

fos/ou a / u/it 


Fig. 72.—Change of Carbon in Cast Iron. 




Q 








VUOJOH JEM- /owmi 




congeal or crystallize, it begins to expel carbon in the form of graphite, and 
this action is supposed to be completed when the metal has cooled to W, at 
which time the product has probably become wholly crystalline, having 
perhaps less than one per cent of carbon left in the combined form, as 
hardening carbon. It is new very granular in its nature, having little or no 
cohesion, and this intermediate granular form will always prevent the rolling 
of steel direct from the melted state. At the temperature W (low yellow) a 
peculiar change occurs in the combined carbon, a large part of it passing 
from the hardening to the cement form, if sufficient time be given at this 
temperature for this to occur. This change in the carbon state is accom¬ 
panied by a remarkable development of sensible heat, causing the color to 
brighten up again, and this phenomenon is known as recalescence. This 
marks the truly plastic state at which it should be worked. As shown in 
Fig. 72 a, there is no appreciable amount of graphitic carbon in steel, it all 
being in chemical combination, but changing from the hardening to the 
cement form, in a falling, and back again for a rising, temperature past 
the critical low yellow heat. 

The presence of the large amount of graphitic carbon in cast iron causes 
it to fuse at a much lower temperature than steel, because of the recombin¬ 
ing of this carbon, chemically, with the iron at this high heat. The fusing 
temperature of steel is higher as the proportion of carbon is less. 















































































































































STEEL 


153 


107. Physical Effects in Steel of the Change in the Combined Carbon at 
a Low Yellow^ Heat.—Hardening and Tempering. —This change in the 
combined carbon of steel from hardening to cement and back again is 
accompanied by a corresponding change in the crystalline arrangement, in 
the appearance of the fracture, and in all its mechanical properties. Thus 
if the region IF— V, Fig. 72a, be passed quickly, as when the specimen is 
quenched in water from a temperature above IF, there is very little change 
in passing this critical temperature, and hence the carbon remains mostly in 
the hardening state. This gives a very hard and brittle product (when the 
percentage of carbon is high, or from 0.75 to 1.0 per cent), and in all cases 
raises the elastic limit and the ultimate strength,* but reduces the ductility. 
The crystalline arrangement, also, is now that which was formed on the first 
cooling, above IF, it being very coarsely crystalline. 

If the region W—V be passed slowly, more especially if the specimen be 
held at this temperature for a considerable period and then cooled slowly, the 
combined carbon changes mostly to the cement state, and a great softening 
of the material results. The only way to retain the carbon in the hardening 
state, when cold, being to cool it quickly from a temperature above IF.f 

When steel has been hardened by sudden cooling from above IF, it can be 
tempered, or softened, by heating again, to some temperature below V and 
cooling slowly. The higher this tempering heat is, below a red heat, followed 
by slow cooling (as in the air), the softer will be the product when cold, as 
the more of the hardening carbon will be changed to the cement state. If 
the reheating be carried to V or above, and cooled slowly, the carbon will be 
(almost) wholly in the cement state, the temper then having been entirely 
drawn. The particular temper required, therefore, is obtained by first 
quenching from IF or above, then reheating to the required temperature 
below V, and cooling slowly. This leaves the required portion of the carbon 
in the hardening state, and gives the product the desired compromise 
qualities of strength, hardness, and ductility, combined with toughness. 

In the matter of the fracture, also, either a slow or a rapid cooling from 
a white heat, without forging or rolling, leaves a coarse crystalline fracture. 

If w r orked down to a red heat it gives a fine crystalline fracture. 

It is of the utmost importance that the heating for both hardening and 
for tempering should be uniform throughout the entire body of the specimen. 
Evidently a liquid bath of some kind furnishes the ideal condition for both 
heating and cooling. Thus a melted lead bath, kept stirred, may be used 
for heating, and a mercury, brine, water, or oil bath for the quenching, or 
sudden cooling. All hardening should be done by quenching from a rising 
temperature, to preserve fineness of grain. The reheating of the hardened 

* Quenching in water from a high temperature may impair the ultimate strength of 
low carbon-steel. Quenching in oil seems always to increase the ultimate strength. 

f If not uniformly heated when quenched, it is apt to break or crack from internal 
stress. The different densities resulting from quenching from different temperatures, 
may furnish a key to this action. 



THE MATERIALS OF CONSTRUCTION. 


154 


steel for the purpose of tempering it may be done by bolding it over a fire, 
or in contact with a heated mass of iron, or in boiling water, or hot steam, 
or in some other way. 

When clean iron or steel is heated in the open air, the oxide which forms 
on the surface takes in succession the following well defined colors, namely: 
light straw, straw, light brown, darker brown, pigeon-wing (a purplish 
brown), light blue, dark blue, and black. In tempering, the final “ temper ” 
depends on which of these graduated colors has been reached, and followed 
by slow cooling. Thus if only the first color indication, light straw, be 
reached, and then the bar slowly cooled, evidently very little softening of 
the hardened steel has resulted, and the product is left very hard, or it is 
said to have a “ very high temper ”; whereas if the highest temperature had 
been reached, at which the oxide had deepened to black, and then the bar 
cooled slowly, it would be found to be quite soft, or the hardness would have 
been entirely removed. The word “ temper” then may have the following 
meanings, according as it is used by the steel-maker or by the steel-user: 


Designation of “ Temper.” 

Steel-maker’s Meaning. 
Percentage of Carbon. 

Steel-user’s Meaning. 

Temper drawn at 

Temperature. 

Name of Color. 

Very liign. 

1.50 carbon 

About 400° F. 

“Light straw ” 

High. . 

1.00 to 1.20 C 

“ 450° F. 

“Straw” 

Medium. 

.70 to .80 C 

“ 500°F. 

“ Brown ” to 




“ pigeon-wing ” 

Mild. 

.40 to .60 C 

“ 550°F. 

“ Light blue ” 

Low. 

.20 to .30 C 

“ 600° F. 

“ Dark blue ” 

Soft, or dead soft. 

Under .20 C 

“ 650°F. 

“ Black ” 


EFFECTS OF CARBON IN ITS VARIOUS STATES ON THE MECHANICAL PROP¬ 
ERTIES OF IRON AND STEEL. 


108. Not Fully Explained by Chemical Analyses. —As shown in Art. 105, 

the mechanical properties of iron and steel are not fully indicated by any 
ultimate chemical analysis of the material, but are dependent on the par¬ 
ticular combinations the elements may have formed. In Art. 106 it was 
further shown that carbon is found in three distinct forms in iron and steel, 
and that the physical qualities depend largely on these particular forms of 
carbon. It is to be expected, therefore, that the mechanical qualities, or 
the qualities shown by the material when resisting the action of external 
forces, would also be found to be greatly dependent on these particular forms 
of carbon, combined and uncombined, or even on the total combined carbon, 
since this has been shown to exist in two very different states. The effort, 
therefore, of students of this subject to harmonize the results of mechanical 
tests with the corresponding ultimate chemical analyses of the materials was 
foredoomed to failure. And since the proximate chemical analysis is as yet 
impossible, we are wholly unable to predict mechanical properties from 




















STEEL. 


J f)5 


chemical analysis alone. When this is supplemented, however, with a full 
knowledge of the heat treatment, as described in the preceding article, some 
approximate knowledge of the mechanical properties is obtained. (See also 
Appendix B. 

109. The Hardening of Steel. —A coarsely crystallized steel may be 
reheated to a temperature between V and IF, and cooled either slowly or 
rapidly, and the fracture becomes finely crystalline or even porcelanic. Just 
what does occur in the hardening of high carbon steel is, and has long been, 
a matter of contention among our most distinguished metallurgical chemists. 
Osmond and his school contend for an allotropic form of iron (called “ ft 
iron,” to distinguish it from the annealed form, which he called “ a iron ”), 
not to be explained by a definite chemical compound, but containing carbon 
in solution, while Prof. Arnold makes a very strong plea for a chemical 
compound, Fe 24 C, which he calls a “ sub-carbide ” (Fe 3 C being the carbide), 
this being he thinks the real composition of steel in a melted state, having 
as much as 0.89 per cent C, which he calls the point of saturation.* When 
this compound is cooled suddenly, this unstable sub-carbide hardens into a 
solid without any change in its chemical composition; but when cooled 
slowly, it passes at 400° C. into the carbide form, with pure iron (Fe ni C = 
Fe 3 C -f- 21 Fe) and with the evolution of heat. See Plates in Appendix B. 

Prof. Arnold gives, as a general summary of his views, the following :f 

I. The constituents of steel may be: (a) Crystals of pure iron which remain 
bright on etching. ( b ) Crystals of slightly impure iron which become pale brown 
on etching, probably owing to the presence of a small quantity of an intermediate 
carbide of h} T pothetical formula FeioC. (c) Normal carbide of iron, Fe 3 C, which 
exists in three distinct modifications, each one conferring upon the iron in which 
it is found particular mechanical properties. (1) Emulsified carbide present in an 
excessively fine state of division in tempered steels. (2) Diffused carbide of iron 
occurring in normal steels in the forms of small ill-defined striae and granules. 
f3) Crystallized carbide of iron occurring as well-defined laminae in annealed and 
in some normal steels. ( d) Subcarbide of iron, a compound of great hardness 
existing in hardened and tempered steels and possessing the formula FeaiC. This 
substance is decomposed by the most dilute acids, and at 400° C. it is decomposed 
into Fe 3 C and free iron with evolution of heat. One of the most remarkable prop¬ 
erties of this compound is its capacity for permanent magnetism. (e) Graphite 
or “ temper-carbon.” % 

The existence of Fe 2 4 C is proved by the fact that iron containing 0.89 per cent 
carbon presents several correlative critical points when examined by different 
methods of observation : (1) Well-marked saturation-points in the micro-structure 

of normal annealed and hardened steels. (2) A sharp maximum in a curve the 
coordinates of which are heat evolved or absorbed in recalescence and carbon per¬ 
centage. (3) A point in the compression curve of hardened steels at which molec¬ 
ular flow absolutely ceases. (4) A sharp maximum in a curve the coordinates of 
which are carbon percentage and permanent magnetism in hardened steels. 

II. The influence of annealing is—(1) To increase the size of crystals and to 
increase the intercrystalline cohesion when originally feeble or impaired. (2) To 
convert elongated masses of iron containing diffused Fe 3 C into compact rounder 

* With as much as 1 per cent manganese he claims the point of saturation with carbon 
is reached with 0.6o C. See Appendix B. 

f Trans. Inst. Civ. Engrs., vol. cxxm, 189G, p. 160. See also Appendix B. 

X Ledebur distinguishes between graphite and temper-carbon. 




156 


THE MATERIALS OF CONSTRUCTION. 


bodies, containing laminae of crystallized Fe 3 C, between which the iron becomes 
more or less dovetailed throughout the mass. 

III. The approximate theoretical constituents of hardened and normal steels will 
be in accordance with the figures given in Table IX. (These percentages, however, 
can never be quite correct, because in practice hardened steels below the saturation- 
point (0.89$ C) always contain a little Fe 3 C, and normal steels below the saturation- 
point a small quantity of the intermediate carbide, Fei 0 C(?) ). It is obvious that in 
tempered steels an almost unlimited variety of constitutions and consequently of 
mechanical properties is possible. 

TABLE IX.—APPROXIMATE THEORETICAL COMPOSITION" OF HARDENED AND 
NORMAL IRON AND CARBON STEELS REQUIRED BY THE SUBCARBIDE 


THEORY HEREIN ENUNCIATED. 


Carbon. 

Hardened Steels. 

Normal Steels. 

Fe. 

Fe 24 C. 

Fe 3 C. 

Fe. 

Fe,C. 

Per cent. 

Per cent. 

Per cent. 

Per cent. 

Per cent 

Per cent. 

0.10 

89 

11 

0 

99 

1 

0.20 

78 

22 

0 

97 

3 

0.30 

67 

33 

0 

95 

5 

0.40 

56 

44 

0 

94 

6 

0.50 

45 

55 

0 

93 

7 

0.60 

34 

66 

0 

91 

9 

0.70 

22 

78 

0 

90 

10 

0.80 

11 

89 

0 

88 

12 

0.90 

0 

100 

0 

87 

13 

1.00 

0 

99 

1 

85 

15 

1.10 

0 

97 

3 

84 

16 

1.20 

0 

95 

5 

82 

18 

1.30 

0 

93 

7 

81 

19 

1.40 

0 

91 

9 

79 

21 

1.50 

0 

89 

11 

77 

23 


IV. The subcarbide theory falls into line with the observations of every-day 
experience. For instance, the fact has long been known that pure carbon steel, con¬ 
taining about 0.85 per cent of carbon, is the most suitable for steel which must carry 
a cutting edge and yet be tough enough to withstand a sudden shock. Such steel is 
therefore employed for cold sets.* It is also well known that a steel containing 1.3 
per cent of carbon would be useless for such a purpose, as it would crack and 
“snip.” The reason is clear; such material is full of lines of weakness along the 
junctions of the subcarbide granules with the surplus normal carbide membranes. 
On the other hand, it is known that a steel harder than one carrying 0.9 per cent of 
carbon is necessary for turning-tools. In such a case no shock has to be encountered, 
so that the surplus Fe 3 C augments the hardness of the subcarbide with its own 
intense hardness, and moreover adds 10 per cent of a substance incapable of 
“letting down” with the heat of friction. It is also clear that a steel with carbon 
much below 0.9 per cent cannot carry a cutting edge, because of the presence of 
particles of soft free iron aumngst the mass of the hard subcarbide. See App. B. 

110. Effect on Tensile Strength. —While a diagram showing the relation 
of tensile strength to percentage of carbon in steel gives a cloud of results 
spread over a wide belt (see Howe’s Metallurgy of Steel, p. 14), yet a 
simple formula which is the algebraic expression of a line which traverses 
this field well below its centre of gravity may be of some use. While many 

__ %j 


* As required in saws. 



























STEEL. 


157 


such formulae have been proposed, that of Salom * seems best to fit the 
total assemblage of results and is easily remembered. It is 

T- 45,000 + 100,000(7,.(1) 

where T = tensile strength of rolled steel in pounds per square inch 
(up to C = 1.0 per cent); 

C = percentage of carbon 

The recorded tests show many results as much as 20,000 pounds per 
square inch above this locus, and some 10,000 pounds below it. It may be 
regarded, therefore, as traversing the lower edge of the middle third of the 
cloud of recorded observations. As the maximum strength of steel is 
reached with C = about 1.0 per cent, the above formula must not be used 
above T — 145,000 and C = 1.0. Higher values of tensile strength, as with 
drawn steel wire, are due to the physical treatment and not to the chemical 
composition. The elastic limit in both tension and compression may be 
taken as 60 per cent of the tensile strength. 

As a result of a careful study of over four hundred tests accompanied by 
their corresponding chemical analyses, made in the regular course of business, 
Mr. William K. Websterf offers the following table, showing the variation 
of strength of soft steel with varying percentages of carbon and phos¬ 
phorus, assuming the manganese and sulphur are each zero. When either 
or both of these latter are present, the values may be corrected by adding 
the values given in the two auxiliary tables for the corresponding percent¬ 
ages of these ingredients. 

TABLE XII.—ESTIMATED ULTIMATE STRENGTH OF STEEL FOR VARYING 
PERCENTAGES OF CARBON AND PHOSPHORUS. J 

On the assumption that neither manganese nor sulphur is present, the tabular values to be 
increased for these ingredients by the amounts given in the two following auxiliary tables. 


Carbon in Parts 
of 1 per cent. 

.06 

.08 

.10 

.18 

.14 

.16 

.18 

.80 

.88 

.24 

Percentage of 
Phos. .030 

39,550 

41,150 

42,750 

44,350 

45,950 

47.550 

49.150 

50,750 

52,350 

53,950 

“ .01 

40,350 

41,950 

43,750 

45,550 

47,350 

49,050 

50,650 

52,250 

53,850 

55,450 

“ .02 

41,150 

42,750 

44,750 

46,750 

48,750 

50,550 

52,150 

53,750 

55.350 

56.950 

“ .03 

41.950 

43,550 

45,750 

47,950 

50.150 

52.050 

53,650 

55,250 

56.850 

58.450 

“ .04 

42,750 

44.350 

46.750 

49,150 

51,550 

53.550 

55,150 

56,750 

58,350 

59.950 

“ .05 

43,550 

45,150 

47,750 

50.350 

52,950 

55,050 

56,650 

58,250 

59.850 

61,450 

“ .06 

44,350 

45,950 

48,750 

51.550 

54.350 

56 550 

58,150 

59.750 

61,350 

62,950 

“ .07 

45.150 

46,750 

49,750 

52.750 

55,750 

58,050 

59,650 

61,250 

62,850 

64,450 

“ .08 

45,950 

47,550 

50.750 

53,950 

57.150 

59.550 

61,150 

62.750 

64,350 

65.950 

“ .09 

46,750 

48.350 

51.750 

55.150 

58,550 

61,050 

62,650 

64.250 

65,850 

67,450 

“ .10 

47,550 

49,150 

52,750 

56,350 

59.950 

62,550 

64,150 

65,750 

67.350 

68,950 

.001 Phos. = 

SO lbs. 

80 lbs. 

100 lbs. 

120 lbs. 

140 lbs. 

150 lbs. 

150 lbs. 

—tf-r-- 

150 lbs. 

150 lbs. 

150 lbs. 


--- VH 

*See Trans. Am. Inst. Min. Engrs., xiv. p. 127, and also Howe’s work as 
quoted above. 

f Trans. Am. Inst. Min . Engrs., vol. xxm. p. 114. 

\ Campbell gives, in his work on Structural Steel, p. 306.- 

Ulfimate strength of acid steel = 33,000 -f- 1485 G 4* 1260 P, 

“ “ “ basic “ = 40,000 -f 1085 (7+ 1200 P. 

G = percentage of carbon and P— percentage of phosphorus 


where 































158 


THE MATERIALS OF CONSTRUCTION ,. 


TABLE XIII.—ADDITIONS FOR SULPHUR IN PARTS OF 

ONE PER CENT. 


Sulphur. 0 .01 

Additions in pounds per square inch. .000 500 


.02 .03 .04 .05 .06 .07 

1000 1500 2000 2500 3000 3500 


TABLE XIV.—ADDITIONS FOR MANGANESE IN PARTS OF 

ONE PER CENT. 


Man. 

Lbs. 

Man. 

Lbs. 

Man. 

Lbs. 

Man. 

Lbs. 

Man. 

Lbs. • 

.15 

3,600 

.27 

6,300 

.38 

8,280 

.49 

9,780 

.60 

10,900 

.16 

3,840 

.28 

6,500 

.39 

8,440 

.50 

9,900 

.61 

11,000 

.17 

4,080 

.29 

6,700 

.40 

8,600 

.51 

10,000 

.62 

11,100 

.18 

4,320 

.30 

6,900 

.41 

8,740 

.52 

10.100 

.63 

11,200 

.19 

4,560 

.31 

7,080 

.42 

8,880 

.53 

10,200 

.64 

11,300 

.20 

4,800 

.32 

7,260 

.43 

9,020 

.54 

10,300 

.65 

11,400 

.21 

5.020 

.33 

7,440 

.44 

9,160 

.55 

10,400 

.66 

11,500 

.22 

5,240 

.34 

7,620 

.45 

9,300 

.56 

10,500 

.67 

11,600 

.23 

5,460 

.35 

7,800 

.46 

9,420 

.57 

10,600 

.68 

11,700 

.24 

5,680 

.36 

7,960 

.47 

9,540 

.58 

10,700 

.69 

11,800 

.25 

.26 

5,900 

6,100 

.37 

8,120 

.48 

9,660 

.59 

10,800 

.70 

11,900 


111. Effect on Ductility. —In general the ductility of steel diminishes as 
the percentage of carbon increases. The ductility is usually determined by 
dividing the total stretch of a specimen between marks eight inches apart, 
which includes the section of rupture, by the original length of eight inches. 
This total stretch is found after the specimen has been broken in tension, 
and is called the “ percentage of elongation.” From the plotted results of 
over one thousand determinations of elongation with known percentages of 
carbon,* the author of this work would express this general relation by the 
formula 

3 

E ~ C° + 0.1’. 


where E — percentage of elongation in eight inches, 

C ~ percentage of carbon (less than 1.00). 

This would seem to give too low a percentage of elongation by about 5 
per cent for carbon from 0.25 to 0.45 per cent. In any case the elongation 
may vary from the mean as given by this equation by at least one fourth of 
its value, showing that the ductility is dependent on other things besides the 
proportion of carbon. 

There seems to be no difference between open-hearth and Bessemer steel 
in this respect, but crucible steel gives an elongation equal to that of the 
other varieties of a lower carburization. In other words, crucible steel is 
more ductile than the cheaper grades, for the same proportion of carbon. 


* Howe’s Metallurgy of Steel, p. 16. 







































STEEL. 


159 


112. Elongation and Tensile Strength. —Mr. Howe gives a table of the 
common greatest and least limits of elongation for various grades of steel, 
which have been plotted in Fig. 73. The shaded area between these limits 
may be regarded as the Elongation Field. In this field has been drawn two 
curves, which are the loci of two equations expressing elongation in terms of 
the ultimate strength. One of these («) has been proposed by a committee 
of the Am. Soc. Civ. Engrs. (July, 1890), and the other ( b ) by the author. 



Fig. 73. —Showing the Elongation Field for Structural Steel and the Loci of Proposed 
Elongation Equations. Limits of Greatest and • Least Elongations taken from 
Howe’s Metallurgy of Steel. 


The former is an equilateral hyperbola, making the product of the ultimate 
strength per square inch and the percentage of elongation a constant, and 
equal to 1,500,000, or 


„ 1,500,000 

E= —J— 



The other is also a hyperbola referred to asymptotes parallel to the main 
axes, but removed from them, as shown in the figure, and whose equation is 


E = 


1,800,000 


f - 10,000 


10 . . 


( 4 ) 


































































160 


TUE MATERIALS OF CONSTRUCTION. 


113. Modulus of Elasticity. —As stated in Art. 11, the modulus of elas¬ 
ticity is not appreciably affected by the percentage of carbon or by any other 
ingredient. This is also shown by Fig. 294. The author of this work be¬ 
lieves that with such determinations of this modulus as have been made 
hitherto, it is rather to be presumed that discrepant values are due to inade¬ 
quate or erroneous methods of determination rather than to actual wide 
departures of the modulus from its mean value. 

114. The Compressive Strength.— The elastic limit is the real ultimate 
compressive* resistance with the softer grades of steel, having a definite 
“ yield-point” (see Fig. 294), while with hard steel there is no yield-point 
and no very definite elastic limit, and the ultimate strength in compression 
is clearly marked by a decided rupture on planes of maximum shearing stress. 
Few tests of steel have been made in compression, but it is shown in Chap. 
XXVI. that the compressive elastic limit is numerically equal to that in 
tension, or as GO per cent of the ultimate tensile strength. In other words, 
the compressive resistance of steel is increased by increasing carbon the same 
as the tensile strength. 

115. Hardness and Fusibility. —The hardness increases tvith increasing 
carbon apparently without limit. 

The fusibility also increases with increasing carbon without limit. Thus 
cast iron and the hard grades of steel melt at a much lower temperature than 
wrought iron and the soft steels. 

INFLUENCE OF SILICON ON IRON AND STEEL. 

116. Combination of Iron and Silicon. —“ Silicon alloys with iron in all 

ratios, at least up to 30 per cent, being readily reduced from silica (Si0 2 ) by 
carbon in the presence of iron. It rarely, if ever, exists in iron in the 
graphitoidal state. It diminishes the power of iron to combine with carbon, 
not only when molten (thus diminishing the total carbon content), but more 
especially at a white heat, thus favoring the formation of graphite during 
slow cooling. It increases the fusibility and fluidity of iron; it lessens the 
formation of blow-holes; by reducing iron oxide it apparently removes one 
cause of red-shortness; it hinders at high temperatures the oxidation of iron, 
and probably of the elements combined with it. Silicon steels with 1 to 2 
or even 2.5 per cent silicon, sometimes excellent for cutting hard steel, have 
been made. Iron absorbs silicon greedily, uniting with it in all proportions 
at least ifp to 30 per cent, and apparently the more readily the higher the 
temperature, absorbing it even at a red heat when imbedded in sand and 
charcoal. Though silica can neither be reduced by iron alone nor by carbon 
alone, it is readily reduced by carbon if iron be present to alloy with the 
resulting silicon. 

“ Silicon may be oxidized by both carbonic acid and carbonic oxide: it is 
removed from molten iron very rapidly by atmospheric air, and by simple 
contact with iron oxide, magnesia, and other bases.” * 


* Howe, vol i. p. 36. 




STEEL. 


161 


117. Influence of Silicon on Physical Properties. —The effect of silicon 
is to increase the strength and to reduce the ductility of steel, as shown in 



Pig. 74.—Physical Properties of Silicon Steel, showing the Effects of Carbon and 
Silicon. (Hadfield in Jour, Ir, & St, hist,, vol. ii. p. 222.) 

JV. 74. It also has a decided effect in increasing the soundness of ingots 
and other castings, thus preventing blow-holes, and by reducing the iron 
oxide it to that extent prevents red-shortness. 

118. Effects on Cast Iron. —The effect of silicon on cast iron is to 
increase its fluidity, and to change the carbon to the graphitic form. Thus 
hard white cast iron is reduced to soft gray iron by the addition of silicon, 
while its tensile strength and its ductility or toughness is increased. 

INFLUENCE OF MANGANESE ON IRON AND STEEL. 

119. In General. —“ Manganese alloys with iron in all ratios, being 
reduced from its oxides by carbon at a white beat, and the more readily the 
more metallic iron is present to combine with it. It is easily removed from 
iron by oxidation, being oxidized even by silica, and partly in this way, 
partly in others, it restrains the oxidation of the iron, while sometimes 
restraining, sometimes permitting, the oxidation of the other elements com¬ 
bined with it. It is also apparently removed from iron by volatilization. 
Its presence increases the power of carbon to combine with iron at very high 
temperatures (say 1400° C.), and restrains its separation as graphite at lower 
ones.* By preventing ebullition during solidification and the formation of 

* Prof J O. Arnold says that with 1 per cent manganese iron becomes saturated 
with 0.65 C. instead of 0.89 C with no manganese. Hence the softer qualities of Swed¬ 
ish steels of a given percentage of C, as they contain only about 0.25 per cent Mo. 

See Appendix B. 














































THE MATERIALS OF CONSTRUCTION. 


163 


blow-holes; by reducing or removing oxide and silicate of iron; by bodily 
removing sulphur from east iron and probably from steel; by counteracting 
the effects of the sulphur which remains, as well as of iron oxide, phosphorus, 
copper, silica and silicates, and perhaps in other ways,—it prevents hot¬ 
shortness, both red and yellow. (It does not, however, counteract the cold¬ 
shortness caused by phosphorus.) These effects are so valuable that it is 
to-day well-nigh indispensable, though admirable steel was made before its 
use was introduced. 

“It is thought to increase hardness proper and fluidity, to raise the 
elastic limit and the ultimate strength, and, at least when present in con¬ 
siderable quantity, to diminish fusibility.” * 

120. Effect of Small Percentages of Manganese on Static Strength.— 
From over 400 tests of the strength of mild steel accompanied by chemical 
analyses, Mr. William It. Webster f estimates the effect of manganese in 
increasing the ultimate strength, as given in the following table: 


TABLE XV. — INCREASE IN ULTIMATE STRENGTH FROM SMALL PERCENTAGES 

OF MANGANESE. 


Manganese, Per Cent. 

Increase in Ultimate 
Strength. 

Total Increase in Ultimate 
Strength from 0 Manganese. 

From 

To 

Lbs. per Sq. In. 

Lbs. per Sq. In 

0.00 

0.15 

3,600 

3,600 

0.15 

0.20 

1.200 

4,800 

0.20 

0.25 

1,100 

5.900 

0.25 

0.30 

1,000 

6.900 

0.30 

0.35 

900 

7,800 

0.35 

0.40 

800 

8,600 

0.40 

0.45 

700 

9,300 

0.45 

0.50 

600 

9,900 

0.50 

0.55 

500 

10,400 

0.55 

0.60 

500 

10,900 

0.60 

0.65 

500 

11,400 


121. Manganese-steel. —“ While the small amounts of manganese in 
ordinary commercial steel increase its forgeableness, and within certain limits 
its brittleness, yet when so much manganese is present that its effects out¬ 
weigh those of carbon, and thus forms a true manganese steel, the alloy 
becomes extraordinarily tough and difficultly forgeable: it possesses a com¬ 
bination of hardness and toughness which should be of value for tools which 
cut by impact, and which is not otherwise attainable, so far as I know, at 
least in any material available for the arts. Several attempts to utilize its 
remarkable properties have been made of late, and others are to be 
expected.” £ 

“ Briefly, manganese-steel of the best composition, with say 14 per cent. 

* Howe, vol i. p. 42. 

f See Trans. Am. Inst. Mining Engineers , vol. xxm. p. 114. 

t Howe, vol. i. p. 48. 











STEEL. 


163 


of manganese and not more than 1 per cent of carbon, is very fluid; 
solidifies rapidly and with great contraction; does not form blow-holes, but 
pipes deeply; does not seem subject to segregation; is forgeable, but welds** 
poorly if at all. Naturally brittle, only moderately strong, and with very 
low elastic limit, it is made extremely tough and very strong* * * § and (under 
impact) stiff by quenching from whiteness, which neither cracks small bars 
of it, changes its fracture (which before forging is strongly crystalline), nor 
greatly raises its elastic limit; this, however, is greatly raised by cold stretch¬ 
ing, only to fall on reheating. Test-bars stretch nearly uniformly, like 
brass, instead of necking like iron. It is so hard that it can barely be 
machined, but it is slightly softened by sudden cooling from very dull red¬ 
ness; is not brittle at blueness, nor (apparently) made brittle by blue-work,, 
but is rapidly made brittle by cold-work, ductility being restored by reheat¬ 
ing and quenching; does not recalesce f during cooling; its density (sp. 
gr. 7.83, for manganese 13.75), modulus of elasticity, and (apparently) its 
rate of corrosion are about the same as those of common iron; its electric* 
resistance is enormous, thirty times that of copper and eight times that of 
wrought iron, but thrice as constant with varying temperature as that of 
iron; it can be magnetized very considerably temporarily, but only with most 
extreme difficulty, and hardly at all permanently.” J 

INFLUENCE OF SULPHUR ON IRON AND STEEL. 

122. In General. —“ Sulphur unites with iron probably in all proportions 
up to 53.3 per cent, being readily absorbed from many sources. It may, 
however, be prevented from combining with iron, and even expelled from it 
by many agents (e.g., basic slags, carbon, silicon, manganese, oxygen, water, 
ferric oxide). Certain of these in the blast-furnace prevent the sulphur 
present from combining with the cast iron, and in the conversion of pig iron 
into malleable iron, whether by puddling, by pig-washing, or by the basic 
process, much of the sulphur of the cast iron is expelled. It causes cast iron 
to retain its carbon in the combined state. Carbon and sulphur and perhaps 
also silicon and sulphur are mutually exclusive within limits. Sulphur 
makes malleable iron red-short and interferes with its welding, but these 
effects are largely effaced by the presence of manganese. It is thought to 
make cast iron harder, though this effect* is at least in part due to its causing 
it to retain the carbon in the combined state. It increases the fusibility of 
cast iron, but makes it thick and sluggish when molten, and gives rise to 

blow-holes during its solidification.” § 

123. Red-shortness.—“ Sulphur has the specific effect of making iron 
exceedingly brittle at a red heat, and of destroying its welding power. Its 

* Tensile strength raised from 80,000 to 100,000 lbs. per square inch, and elongation 
in 8 inches raised from two per cent to forty-five per cent! 

f See Art. 130, (e), for definition of this term. 

\ Ilowe, vol. i. p. 3G1. 

§ Howe, p. 48. 






164 


THE MATERIALS OF CONSTRUCTION. 


effect are in general most marked at a dull-red heat, and irons which crack 
at this temperature owing to the presence of a small percentage of sulphur, 
may often he readily forged at higher temperatures, while when cold they 
are as malleable and indeed often more malleable, than lion-sulphurous irons. 
If, however, the percentage of sulphur is considerable, the iron is no longer 
malleable even at temperatures above redness. The red-shortness imparted 
by a giren percentage of sulphur is probably independent of the percentage 
of carbon which accompanies it; but more sulphur can usually be tolerated 
in steel rich in carbon than in others, because such steel usually contains 
much manganese also. 

“ The rail-steel of our Eastern mills has usually from 0.03 to 0.0G per 
cent sulphur; that of our Western mills has usually somewhat more, occa¬ 
sionally as much as 0.10 or 0.12 per cent, and even exceptionally 0.14 per 
cent. When sulphur is under 0.08 per cent its effects [on red-shortness] are 
probably almost completely effaced by the presence of 0.80 per cent man¬ 
ganese, since with this composition the red-shortness is so slight that T rails, 
the formation of whose thin flanges necessitates great malleablness, can be 
rolled with so little cracking that at some mills only 0.4 per cent of the rails 
made are of second quality (i.e., have cracked flanges). 

“ Pieces of a shape which can be produced without necessitating such 
extreme malleableness as the formation of the thin flanges of T rails requires 
may contain more sulphur; but it is rare to find more than 0.12 sulphur in 
any steel. Crucible tool-steel has ordinarily less than 0.01 per cent. Kail- 
plate has usually from 0.05 to 0.10, boiler-plate from 0.02 to 0.08, per cent. 

“ Manganese counteracts the effects of sulphur. In many cases 4.5 
parts by weight of manganese so far counteract the effects of one part of 
sulphur as to permit the rolling of flange T rails.” * See also Appendix B. 

124. Tensile Strength and Ductility. —The effect of sulphur on the 
tensile strength and ductility of iron and steel has formerly been somewhat 
in doubt. It was known, of course, that by producing red-shortness it may 
indirectly cause weakness of the cold specimen from external or internal 
cracks resulting from the red-shortness in the process of rolling. It has 
now been shown by Messrs. Andrews and Arnold, that as small an amount 
of sulphur as 0.05 per cent , in the form of sulphide of iron , may form in 
thm meshes, and so very greatly reduce the strength and toughness of steel. 
Manganese reduces but silicon magnifies this action. Annealing causes 
these sulphide flakes to collect in masses, thus largely destroying its weaken¬ 
ing effects, f This new and important discovery will serve to explain some 
of the many astonishing failures of steel which have hitherto been entirely 
unintelligible. (See Appendix B.) 


* Howe, pp. 52 and 53. 

f Prof. J. O. Arnold in Trans. Inst. Civ. Engrs., vol. cxxm, 1896, p. 209 ; and Mr. 
Tlios. Andrews in Engineering , Jan. 17, 1896. 





STEEL . 


165 


INFLUENCE OF PHOSPHORUS ON IRON AND STEEL. 

125. In General. —“ Phosphorus, the steel-maker’s bane, unites with 
iron probably in all proportions at least up to 26 per cent, being readily 
absorbed by it, especially at high temperatures and when under deoxidizing 
conditions, from acid phosphates and silico-phosphates. Fortunately it is 
readily removed from iron, especially under strongly oxidizing conditions, 
by contact with strong bases (oxides of iron and manganese, the alkalies and 
alkaline earths) and by basic silicates and even silico-phosphates, by alkaline 
carbonates and nitrates, and by fluor-spar. It is volatilized under many con¬ 
ditions, e.g., when phosphates are heated with carbon (the presence of 
metallic iron more or less completely prevents this volatilization), and when 
molten phosphoric cast iron is brought in contact with alkaline matter or 
(probably) with fluor-spar. In the blast-furnace, however, phosphorus is 
not effectively volatilized, for any which volatilizes immediately recondenses. 
Hence in the blast-furnace nearly all the phosphorus passes into the metal, 
though a little is found in the slag if the deoxidizing conditions be weak. 
In puddling 90 per cent, and in the basic Bessemer process 96 to 99 per 
cent, or even more, of the phosphorus initially present may be removed 
under favorable conditions. 

Phosphorus increases the static strength of low-carbon iron and steel, but 
it greatly reduces its resistance to shock. It increases the elastic limit, but 
reduces the ultimate elongation and contraction. Carbon greatly intensifies 
the bad effects of phosphorus, and silicon may intensify them, but certainly 
to a very much smaller degree if at all. “ Rapid cooling and forging during 
cooling, by preventing the coarse crystallization to which phosphoric iron 
strongly inclines, oppose the effects of phosphorus on ductility. It is certain 
that phosphorus does not always diminish the hot-malleableness of iron, at 
least at moderate temperatures; bu f by increasing the tendenc} to coarse 
crystallization it probably diminishes malleableness at very high tempera¬ 
tures, and especially when the iron has slowly cooled without forging from a 
very high temperature to a somewhat lower though still high one, as this 
seems to be the condition most favorable to coarse crystallization.’ 1 * 

126. The Condition of Phosphorus in Iron. —“ In ingot metal phosphorus 
exists chiefly if not exclusively as phosphide, but in weld metal it probably 
■exists both as phosphide and as phosphate, i.e., as part of the mechanically 
intermixed slag, in which condition it is reasonable to suppose that its effect 
on the mechanical properties of the metal should be comparatively slight. 
Many and perhaps an indefinite number of phosphides of indeterminate com¬ 
position may exist in iron, for we find wide differences between the chemical 
behavior of different portions of phosphorus, even in one and the same piece 
of iron, and apparently equally wide discrepancies between the effect of a 
given quantity of phosphorus on the physical properties of different irons. 


* Howe, p. 54. 





166 


TEE MATERIALS OF CONSTRUCTION. 


The differences in the chemical behavior of phosphorus are exemplified by 
the fact that, on dissolving some steels in chlorhydric acid, part of the phos¬ 
phorus escapes as pliosphoretted hydrogen, part is found as phosphoric acid, 
part apparently as some lower oxygen acid, while still another part is 
insoluble. 

“ The existence in solid iron of a definite phosphide of iron, Fe a P, and 
probably that of a definite phosphide of manganese, Mn 2 P 3 , is well estab¬ 
lished.” * 

127. Effect of Phosphorus on the Ductility of Soft Steel. —While phos¬ 
phorus seems to increase the strength of low-carbon steel, it very much 
diminishes its ductility, and this is now regarded by engineers as a very 



Fig. 75.—Effect of Phosphorus on the Ductility of 0.10# to 0.20# Carbon Steel. Num¬ 
bers indicate No. of Observations averaged. (Howe’s Steel, p. 68.) 

dangerous ingredient, and its maximum percentage is carefully specified in 
the better grades of structural steel. Fig. 75 illustrates this effect on steel 
having from one tenth to one fifth of one per cent carbon (0.10 to 0.20) and 
a tensile strength of from 55,000 to 64,000 lbs. per square inch, when the 
phosphorus ingredient is less than one tenth of one per cent. The locus 
drawn on,,this diagram is the most probable curve, showing the law of 
decrease in ductility for increase in phosphorus for the 144 tests here 
plotted. Each plotted point represents the average of the number of tests 
indicated in the attached numerals. W hen the phosphorus ingredient 
reaches one fourth of one per cent the tensile strength of the same steel is 
upwards of 70,000 lbs. per square inch. The diagram in this figure shows 
a loss of ductility represented by a diminished elongation in a length of eight 
inches from 30 pei cent down to 10 per cent, as the phosphorus ingredient 
rose from two one-hundredths to thirty-five one-hundredths of one per cent. 


" Howe, p. 55. 




























STEEL. 


167 


While this diminution of the percentage of elongation for increasing per¬ 
centages of phosphorus is a strong proof of increased brittleness, various 
impact tests on high-phosphorus steel, and surprising and remarkable acci¬ 
dents with such steel, lead to the conclusion that the brittleness of high- 
phosphorus steel under suddenly applied loads and under shock is even 
greater than would be indicated by the diagram in Fig. 75. The maximum 
proportion of phosphorus now (1896) allowed under the better specifications 
for structural steel is from four one-hundredths to eight one-hundredths of 
one per cent. This requirement is readily complied with by the basic open- 
hearth process. 

128. Effect of Phosphorus on Static Strength. —From over 400 determi¬ 
nations of strength with corresponding chemical analyses, Mr. William R. 
Webster has shown * that phosphorus adds to the static strength of low- 
carbon steel approximately as indicated in the following table: 


TABLE XVI. — EFFECT OF PHOSPHORUS OX STATIC STRENGTH. 


For Carbon. 
Hundredths Per Cent. 

Increase of Ultimate Strength per 
0.01 Per Cent P added. 

Effect of Unit of P to Unit 
of C as 1 to— 

9 

900 


10 

1000 

H 

11 

1100 

if 

12 

1200 

n 

13 

1300 

n 

14 

1400 

if 

15 

1500 

1 7' 

iff 

16 

1500 


17 

1500 

n 


129. Limiting Values of Chemical Constituents Allowable. —Since nearly 
all the constituents of iron and steel are more or less injurious, it is well to 
specify the upper limits which will be allowed in a given product. These 
upper limits should also be placed as low as possible without increasing 
appreciably the cost. Metcalf f gives, in his work on Steel (1896), the 
following as such a set of limits: 


“ Silicon... < .10 of one per cent. 

Phosphorus. <.05j 

Sulphur. < .02 

Manganese. < .50, or even < .30 

Copper. < .03 


Carbon to meet the physical requirements.” 

* See Tram. Am. Inst. Mining Engineers , vol. xxm. p. 114. 

f Wm. Metcalf, past President Am. Soc. Civ. Eugrs., who has spent his life in 
manufacturing steel, and hence whose judgment in such matters can be relied on. 

\ The specifications put out in 1896 by the Association of American Steel Manufac¬ 
turers contain limitations of the phosphorus ingredient of 0.04 for rivet and fire-box 
steel ; 0 06 for flange or boiler steel ; of 0,08 for raflway-oridge steel ; and of 0.10 for 
steel for buildings and highway bridges. (See Appendix D.) 

















168 


THE MATERIALS OF CONSTRUCTION. 


The following chemical requirements were adopted by the Illinois Steel 
Co. for steel plates in 1895: 


Quality. 

Carbon. 

Manganese. 

Sulphur. 

Phosphorus. 

Fire-box. 

.16 

. 35 to . 50 

Not over .040 

Not over .020 

Boiler. 

18 

.35 to .60 

“ “ .045 

“ “ .040 

Flange . 

.18 

.35 to .60 

“ “ .045 

“ “ .040 

Ship.. • • 

.15 

.35 to .65 

“ “ .060 

“ “ .080 

Tank. 

.10 

.40 

“ “ .100 

“ “ .120 


HARDENING. TEMPERING, AND ANNEALING. 

130. Heat Changes in Carbon Steel.—When steel contains from 0.50 to 
1.00 per cent carbon it crystallizes in a number of ways, and the ingredients 
arrange themselves in a number of different chemical combinations at differ- 
ent temperatures. The changes in the structures of steel when passing 
through the critical temperatures are discussed in Art. 107. Thus there is a 
critical temperature between a cherry-red and a low-yellow heat (about 700° C. 
or 1300° F.), at which the state of the carbon changes from cement to com¬ 
bined (or hardening) carbon as the temperature slowly rises past this point, 
and from hardening to cement again as the temperature slowly falls below it. 
Thus at temperatures above 700° C. the carbon is all in the hardening state,, 
and the crystallization is that which corresponds to this chemical combina¬ 
tion. When the temperature slowly falls below this limit, however, the 
carbon is expelled from its former associations, the metal arranges itself in a 
new series of crystals, and this state of transition is marked by many peculiar 
phenomena. 

(a) At this time, whether the passage through this transforming region 
be upward or downward, the metal shows great weakness. The molecules 
seem to largely loose their coherence, and the Oar bends readily, or the metal 
flows freely under a comparatively low stress. After passing this stage, in 
either direction, the strength is greatly increased. 

(b) When this stage is reached with a rising temperature, or when the 
cement carbon is changing to the combined or hardening state, a great deal 
of heat is consumed to effect this change, so that notwithstanding the con¬ 
tinued absorption of heat the temperature ceases to rise for a time. That is 
to say, the heat added here becomes latent, or does work in effecting the 
change in the carbon condition and the new arrangement of the crystals. 

When this stage is reached with a falling temperature, the carbon 
separates itself from its former chemical union with the iron, and forms a 
new compound (Fe 3 C, carbide of iron), and the carbon is now said to be in 
the cement state. This involves a new crystalline arrangement also, a tem¬ 
porary weakening of the metal, and a giving out of the latent heat as sensible 
heat. That is to say, as the bar cools down past this point its temperature 






















STEEL 


169 


suddenly increases, though in a cooling atmosphere, from the transformation 
of the latent to sensible heat. This action is called recalescence. 

(d) As a result of this increase in temperature the contraction is changed 
to an expansion, to be followed by a contraction when the temperature begins 
falling again. 

O £5 

131. Hardening of Steel.—In order to obtain a hardened steel it is 
necessary to retain the carbon in the hardening state (chemically combined 
with the iron in the ratio of about 99 Fe to 1 C) when cold. Although the 
carbon always is in this state at high temperatures (above about 1300° F.),. 
yet it will always change from this to the cement state in falling through 
this critical temperature, if any appreciable length of time is given it to effect 
the corresponding chemical and structural changes. It follows, therefore, 
that hardening consists in cooling steel rapidly from a temperature above a 
low-yellow heat , in order that it shall not have time to effect these changes. 
Doubtless a portion of this change does occur, but with very sudden cooling 
in a liquid bath most of the carbon is retained in the hardening form. The 
degree of suddenness of cooling depends on the kind of liquid used; hence 
the great variety of cooling baths in use, such as mercury, salt-water, fresh¬ 
water, oil, tallow, tar, etc. These liquids cool the steel with a relative 
rapidity in the order here named, mercury cooling it most rapidly. 

132. Tempering of Steel.*—Having cooled a piece of steel suddenly, and 
so retained its carbon in the hardening state, it is usually found to be too 
hard and brittle for the mechanical uses to which it is to be put. It must 
now be softened, or tempered, by heating it up to the proper temperature, 
and cooling slowly, which will suffice to change a certain portion of the 
carbon into 'the cement, or carbide, form. Evidently the higher this tem¬ 
perature the more complete will be this change. Even though in tempering 
the heat should reach the critical low-yellow stage, where the carbon takes 
on the hardening form, if it be followed by slow cooling, as in the air, it will 
change back to the cement state, and the piece will be entirely softened, or 
annealed. When the reheating is well below this critical temperature, and 
followed by slow cooling, the piece will be softened in proportion to the 
temperature reached and to the time during which it was kept at such tem¬ 
perature. Thus any particular degree of hardness, or temper, can be 
obtained by intelligent and skilful handling. 

133. Effects of Hardening and Tempering.—The effect of hardening, 
that is, of sudden cooling of steel containing 0.50 per cent carbon or more, is 
to retain the carbon mostly in the hardening state, and to give a degree of 
hardness proportioned to the percentage of carbon and the suddenness of the 
cooling. Not only is the product harder, but its strength and its elastic 


* The word “temper” is used in two senses. The steel-maker uses it to indicate 
initial hardness, as produced by the percentage of carbon, as low, medium, or high tem¬ 
per. The user of steel uses this term to indicate final hardness, as determined by the 
heat (color) to which hardened steel was reheated, as straw, brown, blue, etc. (See table 
in Art. 107.) 




170 


THE MATERIALS OF CONSTRUCTION '. 


limits under all kinds of stress is greatly increased. The ductility, however, 
is reduced as the strength is increased. Thus steel containing 0.50 per cent 
C, which cooled in the air after rolling at a red heat, having a normal tensile 
strength of 67,000 lbs., an elastic limit of 34,000 lbs. per square inch, and 
an elongation in eight inches of 25 per cent, when heated to a low-yellow 
heat and quenched in water will have its tensile strength raised to 150,000 
lbs. per square inch, an increase of 73 per cent; its elastic limit raised to 
68,000 lbs. per square inch, an increase of 100 per cent; and its elongation 
reduced to 2.5 per cent, a loss of 90 per cent. Such a steel can now be 
tempered and brought to any condition intermediate between these limits. 
When hardened in oil all the above effects are less marked. 

134. Annealing consists in heating to or slightly above the critical point 
described in the preceding articles, that is, to a medium average color (or 
655° C. or 1150 a F.), and cooling slowly and uniformly. This removes all 
the hardening effects of a previous rapid cooling, and it also removes all the 
internal stresses produced by a previous unequal heating and cooling, as 
when portions of the plate have been heated for forging, and also the effects 
•of such hot or cold working, as rolling and hammering when hot, or punch¬ 
ing, shearing, bending, pulling, crushing, hammering, twisting, rolling, etc., 
when cold. That is to say, proper annealing restores the metal to its normal 
condition. In the case of steel, it changes all the carbon to the cement or 
non-hardening condition, and at the same time relieves all internal stresses. 
To insure its full effects, however, the cooling should be slow and uniform 
through the entire mass of the body. It should not, however, be left to cool 
down with the furnace, as this holds it too long at the high temperature. 
It should be removed from the furnace as soon as heated through, but may 
then be covered with quick-lime or powdered charcoal, to insure a slow and 
even cooling. Merely heating to the required temperature and cooling in 
the open air, possibly in contact with cold metal surfaces, and exposed to 
draughts, does not satisfy the necessary conditions of proper annealing, since 
the cooling is too rapid and is wanting in uniformity. The heating should 
be in an oven large enough to take the entire body, and not by a forge, or 
by a fire built over the body, and the rate of heating should not be too 
rapid. 

Wire is usually annealed in cylindrical pits built of fire-brick, and covered 
over, the fire passing around them. This, and all other processes of anneal¬ 
ing in which the steel is exposed to the air, causes an oxide scale to form on 
the exposed surfaces, which scale has then so strong an affinity for the 
carbon of the underlying steel, that it decarbonizes it to a very slight depth 
below the scale. While this is of no consequence in large masses, as in 
structural forms or in billets, it is quite fatal in such cases as fine spring-wire, 
or wire to be made into drills, punches, graving-tools, and the like, as this 
decarbonized surface cannot be hardened. To prevent this action the 
annealing-pots are commonly filled with charcoal, which serves both to 
exclude most of the air and to deoxidize what is left, but still some oxidation 




STEEL. 


171 


of the steel surfaces occur, with a corresponding decarburization be¬ 
neath it.* This process also fails to give perfect results, and some other 
means must be found. 

The Jones method (patented) consists in putting material in a closed 
tube from which the air is all expelled by some other non-oxidizing gas, and 
then placed in the furnace, and turned occasionally, the gas constantly flow¬ 
ing through the pipe. This seems to he a perfect method, the surfaces 
remaining absolutely bright and untarnished. 

Metcalf uses a closed pipe also, with a loose cap, with resin thrown into 
the extreme end, which, by volatilizing on first entering the furnace, drives 
nearly all the air out of the tube. While this method leaves the surface 
slightly tarnished it prevents all decarburization of the steel. 

CORROSION. 

135. Corrosion of Iron and Steel. —Iron is corroded by the combined 
action of oxygen and water or carbonic acid and water. Neither of these 
elements acting alone will start corrosion on iron. Iron will remain bright 
indefinitely in dry air, or in water free from oxygen and carbonic acid. 
Acid fumes, sulphuretted hydrogen, chlorine, etc., will start corrosion with¬ 
out the presence of water. After a rust coating has once formed, however, 
it will progress in dry air. Corrosion proceeds more rapidly when the sur¬ 
face is alternately wet and dry, or when the moisture coating is very thin, 
than when deeply immersed. 

While cast iron resists corrosion better than wrought iron and rolled 
steel, when all these have their natural surfaces unbroken, yet if all be 
dressed, and the bright surfaces exposed, cast iron corrodes more rapidly 
than the rolled metal. No relation has been established between the chemi¬ 
cal composition of iron and steel and the rate of corrosion. Neither can it 
be affirmed that wrought iron or steel corrodes the more readily. (See 
Howe’s Met. of Steel, §§ 160-169.) 


* Metcalf says it is very common to maintain the heat too long in using this and other 
methods of annealing, thus spoiling vast quantities of good steel every year. Some of 
the carbon changes to the graphitic form when the heat is too long maintained.— Steel, 
p. 88. 




CHAPTER X. 


THE MINOR OR AUXILIARY METALS OF CONSTRUCTION AND 

THEIR ALLOYS. 

THE MINOR METALS. 

136. Copper.— Copper, being found native, has been used in the arts,, 
both alone and alloyed with tin and zinc, from the earliest times. It is so 
commonly used now for electric conductors that its more important qualities 
are well known. Its specific gravity is from 8.6 in castings to 8.9 in rolled 
and drawn forms, giving thus an average weight of 550 lbs. per cubic foot. 
It melts at about 2000° F., volatilizes at a white heat, and when cold does 
not oxidize in dry air, but does in a moist or acid atmosphere. It unites- 
with oxygen at a red heat, forming both the black and the red oxides, the 
latter of which is soluble in melted copper, and makes it brittle when cold. 
Commercial copper is never pure,* the ordinary ingredients being iron, 
arsenic, antimony, and the red (cuprous) oxide. This last can be removed 
by melting the copper with charcoal and stirring with a stick of green wood, 
this process being called “ poling.” 

Cast copper has a tensile strength of some 25,000 lbs. per square inch, 
with a very low elastic limit, of some 8000 lbs. When rolled, or drawn into 
wire, its strength may be raised to 50,000 or 60,000 lbs. per square inch, 
depending on the amount of work done upon it. It is then “ hard-rolled” 
or “ hard-drawn,” and it has very little ductility. Its elastic limit is then 
very nearly equal to its ultimate strength. By heating it a bright cherry- 
red and cooling it either slowly or quickly, it becomes softened again, or 
annealed. 

137. Zinc, which is commonly called “spelter” when cast, is a hard, 
brittle, white metal, with a highly crystalline fracture. It becomes malleable 
and ductile at about 200° to 300° F., but is brittle again at higher temper- 
tures. Its specific gravity is 6.9 cast and 7.1 rolled. It melts at 800° F., 
and volatilizes at about 1900° F. It rapidly oxidizes in air at a red heat, 
and at a bright red heat, at which copper melts, zinc distils. It is mostly 
used as an alloy in brass, German silver, etc., and as a coating to iron and 
steel sheets and wire, which process is called galvanizing. It is a common 


* The Lake Superior coppers are among the purest in the world. 




THE MINOR METALS AND THEIR ALLOTS. 


173 


electropositive element in electric batteries. Its common impurities are 
iron, lead, and arsenic. 

138. Tin. —Tin is a white, lustrous, and extremely malleable metal, as is 
evidenced by its form in tin-foil. Its specific gravity is 7.3; it melts at 450° 
F., but does not readily volatilize. Commercial tin contains various portions, 
of many elements such as lead, iron, copper, arsenic, antimony, bismuth, 
tungsten, and sometimes manganese and zinc. It is used for coating iron 
plates, and to alloy with copper and zinc. Its low melting-point causes it. 
to be used for safety-plugs in boilers, as its melting-point corresponds to a. 
steam-pressure of about 400 lbs. per square inch above atmospheric. 

139. Aluminum * is a white, soft, malleable metal of extreme lightness, its 
specific gravity being only 2.5G when cast and 2.75 when rolled. It melts 
at about 1150° F., but does not volatilize at ordinary melting temperatures.. 
It is especially free from oxidation and corrosion in air, as neither oxygen, 
carbonic acid, carbonic oxide, sulphuric or nitric acid, sea-water, nor sulphu¬ 
retted hydrogen has much effect on it. It is, however, readily dissolved 
by hydrochloric acid and by caustic alkalies. Its strength pure, when cast, 
is only about 18,000 lbs. per square inch, with low elastic limits in tension and 
compression. When rolled or drawn into wire its strength is raised to from 
25,000 to 50,000 lbs. per square inch with elastic limits of about one half 
the ultimate strength. It is seldom used in a pure state because of its 
softness, but makes with copper, iron, zinc, and tin remarkably strong and 
malleable alloys, which will be discussed as aluminum alloys. 

Aluminum may be rolled either hot or cold. It is annealed by bringing 
it to a low red heat and cooling slowly. In casting aluminum care must be 
taken to provide for the great shrinkage. It is best to cast in hot iron 
moulds and to cool from the bottom artificially, keeping melted metal 
supplied at the gate to supply the shrinkage. Casting under pressure also> 
gives good results. 

It is difficult to obtain aluminum in a perfectly pure state, and very 
slight amounts of impurities largely affect its properties. The common 
impurities are iron and silicon. It is now (189G) supplied regularly by the 
Pittsburg Reduction Company, under a guarantee of 98 $ pure at 50 to 55 
cents a pound, and will be furnished 99$ and 99.6$ pure at special rates. 

THE ALLOYS. 

140. Nature of Metallic Alloys. —Any permanent mixture of two or more 
metals is termed an alloy.\ Neither the appearance nor the mechanical 
properties of an alloy can be predicated upon those of the constituent metals,, 
and the surprising character of the results produced by various mixtures has. 
led to an enormous number of specially named products, each possessing 
certain desirable qualities, the ingredients usually being, for a time at least, 

* See a valuable paper on “Aluminium and its Alloys” in Jour. Assoc. Eng. Socs. y 
vol. xx. p. 1. 

f When mercury is one of the constituent metals the product is termed an amalgam. 





174 


TI1E MATERIALS OF CONSTRUCTION. 


trade secrets. Between 1875 and 1880 the U. S. Test Board made so 
thorough an examination of all possible mixtures of the more usual ingredi¬ 
ents found in alloys (copper, zinc, and tin), that the proprietary or trade 
names formerly used exclusively for these products are now giving place to 
stated percentages of the constituent metals. 

In a general way, mixtures composed almost exclusively of copper and 
zinc are termed brass, while those composed mostly of copper and tin are 
called bronze, while compositions of all three of these elements are called 
composition metal, or perhaps also bronze. All these terms are used loosely, 
however. 

An alloy, though ever so uniformly mixed when in a melted state, is 
usually a conglomerate mixture, after cooling, analogous with granite. 
Some pure chemical unions are formed, and certain substances may crystallize 
out, leaving the more fusible solution or mechanical mixture to form the 
matrix for the entire mass when cold. In most cases there is a decided 
tendency for the metals to separate before cooling, especially when they are 
of different specific gravities, this separating action being called liquation. 
To prevent this the mixture is stirred vigorously just before pouring, which 
is done at as low a temperature as possible. The quicker the metal cools in 
the mould, also, the better, so that it is common to cast alloys in iron moulds 
in order to chill the metal, or to cool it suddenly. To obtain constant 
mechanical qualities in any given alloy seems to be almost a practical 
impossibility. To secure even approximately uniform results requires more 
care and expert superintendence than the manipulation of any single metal. 
The greater the number of the constituent metals, also, the greater are the 
■difficulties encountered. Manufacturers should be slow, therefore, to con¬ 
tract for alloys having definite mechanical qualities of a high order, if they 
have not had a considerable experience in meeting with similar demands.* 
Almost as much seems to depend on the manipulation as on the metals and 
proportions employed; but this subject is too large to be entered upon here.f 

141. The Copper, Zinc, Tin Alloys. —In a general way, some alloy of two 
or more of these metals, copper being always one, is used for all purposes 
where strength, hardness, or malleability is desired in a non-corrosive metal. 
In other words, zinc and tin, one or both, are added to copper to harden and 
strengthen it. Formerly an alloy was used also for large cast guns (then 
called gun-metal), but these are now made of hollow-forged steel. xVs shown 
by Fig. 76, the valuable alloys are those in which copper forms the control¬ 
ling element. This diagram is based on that principle in geometry which 
makes the sum of the normals from any point on the interior of an equi¬ 
lateral triangle equal to the altitude of the triangle. If the three altitudes 
be each taken as a scale of equal parts on which are indicated proportions (per¬ 
centages) of copper, zinc, and tin respectively, these ranging from zero to 

* The author lias known of many failures of contractors in this field. 

f See Mixed Metals , by Prof. Hiorns, 1890, Macmillan & Co. 






THE MINOR METALS AND THEIR ALLOYS. 175 

100, then to the same scale the sum of the three normals from any point in 
the triangle will be 100, and hence these three normals may he used to indi- 
cate the percentages of the three metals which unite to form that alloy which 
is represented by that point in the triangle.* An alloy of any two of these 
finds its place along one side of the triangle, of which the three apices make 
the 100-per-cent ends of the three metal scales. A little study of Fig. 7G 
will make this clear. 


dhe contoui-lines on this figure were drawn by the author after plotting 
on this tiiangle the tensile strengths of cast bronze of known composition 



77/1/ Z//7^ 


Fig. 76. —Showing the Tensile Strength of the Cast Copper-Tiu-Zinc Alloys of all 
Possible Mixtures. (Plotted by the author from the results of tensile tests reported 
by the U. S. Test Board in 1881.) 

from all reliable sources. Dr. Thurston’s chart, after which this is modelled, 
was made from torsion tests by using a constant factor to reduce to equiva¬ 
lent tensile strength. The author finds the tension tests themselves do not 
agree very well with the values given on that chart, and hence he has drawn 

* This method of representing these triple alloys was first used by Dr. R. H. Thurston, 
Trans. Am. Soc. C. E., 1881. 

















176 


THE MATERIALS OF CONSTRUCTION. 


a chart from the tension tests themselves. It must be understood, however, 
that, as stated in the previous article, so much depends on the purity of the 
ingredients, and on the manipulation of the process of melting and casting, 
that this chart, or any similar record, must be taken as showing what may be 
obtained rather than as what will be obtained from the use of these particular 
mixtures. 

THE BRASSES. 

142. The Brasses—Copper and Zinc. —The most valuable brass alloys con¬ 
tain from 65 to 85 per cent of copper and 35 to 15 per cent of zinc (3 to 5 
of copper to 1 of zinc). These mixtures are all strong and ductile, not too 
hard to be readily worked in the lathe (a little tin, say 2 per cent, helps it 
for this purpose), are readily rolled into plates and drawn into wire, and 
under various names are the brasses of commerce. The French standard 
mixture for sheet brass is 67 Cu to 33 Zn (2 Cu to 1 Zn), and care is taken 
to use only the purest metal for this purpose, as a very slight amount of iron 
or silicon (or lead in case of wire-drawing) greatly lessens its ductility. 
Eolled or hammered brass is annealed by heating to a cherry-red and cooling 
either slowly or rapidly. 

Muntz-metal and Sterro-metal are used for ship-coverings in place of 
copper. The former contains 3.8 per cent of zinc, the large proportion of 
zinc producing a corroded surface which prevents the attachment of 
barnacles. The latter contains, in addition, 1.5 to 2 percent of iron, which 
greatly strengthens it. It is also used for hydraulic cylinders carrying 
very great pressures. 

Brass Castings should contain some tin when used for bearings, as this 
increases the hardness. Two or three per cent is sufficient. One or two 
per cent of lead increases its adaptation to turning, filing, and polishing, 
while from 1 to 6 per cent aluminum adds greatly to its strength and duc¬ 
tility. 

In all cases, when melting copper, brass, or bronze, great care must be 
exercised to keep the air from the metal, in order to prevent oxidation. 
This is done by covering the metal, in the crucible, with a- thick layer of 
powdered charcoal. The copper is first melted alone, in a deoxidized flame, 
and then the scrap brass and zinc (previously melted, these fusing at a much 
lower temperature) are added and the whole stirred vigorously to effect a 
thorough'mixing. Sometimes this mixing is done after the crucible is 
removed from the furnace. If it is done in the furnace, the dampers should 
be nearly closed to prevent an excessive heat, which would vaporize the zinc. 

A new brass-melting furnace is shown in Fig. 77,* in which crucibles are 
not used. The metal is charged at the upper door upon a sloping hearth 
from which it falls, when melted, upon the hearth proper, from which it is 
drawn from the tap-hole as shown. The flame from the adjacent fire can 

* Designed and built by J. W. Bennett & Co., Pittsburg. From Engr. News, Oct 1 







THE MINOR METALS AND THEIR ALLOYS. 


177 


be turned into either of these chambers by the opening of suitable dampers, 
or into both at once, or stopped off entirely by the damper at the top of the 
flue. A furnace having 600 to 800 lbs. bosh capacity (5000 to 6000 lbs. 
per day) occupies a space of only 30 to 40 sq. ft. By means of the top 
damper the character of the flame may be so controlled as to prevent exces¬ 
sive oxidation. 

If iron moulds are used, they should be heated and the interior surfaces 



Fig. 77.—A New Brass-melting Furnace. 


coated with a mixture of resin (3 pts.) and lard-oil (1 pt.) to prevent adhe¬ 
sion. In pouring, the metal must be very carefully skimmed. The pattern 
should be made to allow a shrinkage of 1 in. per foot. For common cast¬ 
ings green sand is used, but for fine work the moulds are dried. 

143. Delta-metal, which is an improvement on sterro-metal, is a pro¬ 
prietary comj^osition, or brass, placed on the market since 1883 by a Mr. 
Alexander Dick (England), who used the Greek form of the initial letter of 
his own name to designate his product. His process consists in incorporating 
a fixed amount of iron by making first a saturated solution of iron (about 5 
per cent) in molten zinc. To prevent all oxidation a little phosphorus is 
added to the melted copper. The proportions are varied for different pur¬ 
poses, having from 50 to 65 per cent copper, 50 to 30 per cent zinc, 0.1 to 
5 per cent iron, and sometimes 0.1 to 1 per cent tin. This metal is as strong 
and ductile as mild steel, having a tensile strength, when rolled and annealed, 
of from 60,000 to 80,000 lbs. per square inch, with elongations in eight 
inches of from 40 to 14 per cent, respectively, at these limits." AA hen cast 


* Tests made at Lloyd’s Proving-house, as given by lliorns. 
























































178 


THE MATERIALS OF CONSTRUCTION. 


in sand its tensile strength is 45,000 lbs., with an elongation of 10 per cent. 
It also resists corrosion perfectly. 

144. Tobin Bronze is very similar to sterro-metal and delta-metal, the 
iron ingredient being somewhat less. Its composition is approximately 60 
per cent copper, 38 per cent zinc, 1 to 2 per cent tin, with small portions 
(0.1 to 0.3 per cent) of iron and lead. Its remarkable properties are due to- 
its rolling and annealing. As placed on the market,* its tensile strength is 
from 60,000 to 80,000 lbs. per square inch, with an elastic limit of 60 per 
cent of its ultimate strength, and an elongation of from 25 to 15 per cent in 
eight inches at these limits respectively. It may be regarded as having all 
the mechanical qualities of structural steel, with the advantage of being non- 
corrosive. It can be procured in sheets from -fa inch to 1| inches thick, 
and in round rods from £ inch to 5 inches in diameter. It is readily forged 
at a cherry-red heat either by hand or by machinery. It also works well in 
the lathe. It seems, therefore, to be a practically perfect non-corrosive, 
engineering metal. 

THE BRONZES. 

145. The Bronzes—Copper and Tin. —Since tin is added to copper solely 
to harden it (it strengthens it very little), the copper-tin bronzes may be re¬ 
garded as a kind of hardened copper. The ancients used this combination 
for their cutting-tools, and it is used largely at the present time to produce 
a very hard, non-corrosive metal, useful for many engineering purposes. 
If more than 25 per cent tin is used, the alloy, though hard, becomes very 
weak and brittle. The most common mixture is that of gun-metal , which 
consists of 90 per cent copper and 10 per cent tin. If more than 5 per cent 
tin is used, the metal loses most of its malleability when cold. With about 
20 per cent tin the metal is very hard and sonorous, making it suitable for 
bells, gongs, and wind-instruments. The copper-tin alloys are annealed by 
sudden cooling, as by quenching in water from a red heat, while by slow 
cooling they are hardened. They differ in this respect from nearly all other 
metals. 

By using 33 per cent tin (2 copper to 1 tin), a beautiful, hard, perfectlv 
white alloy is produced, called speculum-metal , suitable for polishing for 
mirrors. \ 

146. Phosphor-bronze is a plain copper-tin alloy made by using a little 
phosphorus as a deoxidizer. It is also claimed that the phosphorus causes 
the tin to form a crystallized compound with the copper. It is mainly, how¬ 
ever, as a cleanser of the melted metal from the oxide of copper that it is 
valuable. When used properly it forms a slag, and is skimmed off; and is 
not found in the finished product. The phosphorus is added in the form 
of phosphor-copper or pliosphor-tin, these containing phosphides of copper 

* By the Ansonia Brass and Copper Co., New York, 
f Lord Ross’s great telescopic reflector was made of this alloy. 






THE MINOR METALS AND THEIR ALLOYS 


179 


or of tin. For a malleable product, to be rolled or drawn into wire, the tin 
should not exceed 4 or 5 per cent, and the phosphorus should not exceed 
one P er cent. For hard castings of great strength, as for pinions, 
valves, bearings, or bushings, use 7 to 9 per cent of tin and \ to 1 per cent 
of phosphorus. A greater amount of phosphorus, up to 4 per cent, increases 
the hardness and brittleness. More than 4 per cent phosphorus will make 
the product useless. 

147. Silicon-bronze is now used extensively in Europe for electric con¬ 
ductors, as it has 70 per cent of the conductivity of copper, wdiile phosphor- 
bronze has but 30 per cent, and steel 10.5 per cent. By using silico-bronze 
wires the poles may be put much farther apart than when copper wires are 
used. While the proportion of silicon remaining in the alloy is very small, 
it has an excellent cleansing action, like phosphorus, without danger of devel¬ 
oping brittleness. The “dose” of silicon, to be added to the melted copper 
or bronze, is prepared by the inventor, Weiller, as follows: “ Take potassium 
silico-fluoride 450 parts by weight, powdered glass GOO parts, common salt 
250 parts, carbonate of soda 75 parts, carbonate of lime 60 parts, and dried 
chloride of calcium 500 parts. Heat these in a covered plumbago crucible 
a little below the temperature where they begin to act on each other, when 
the whole is added to the melted copper or bronze, and vigorously stirred.” 
The resulting slag is skimmed off. 

148. Aluminum Bronze has now come to be regarded as one of the most 
valuable made. It is composed of from 5 to 12 per cent aluminum with 
from 95 to 88 per cent of copper.* These alloys have remarkable ductility, 
combined with great strength. Thus the 5 to 7j- per cent aluminum bronzes 
have, when rolled or forged, an ultimate tensile strength of from 70,000 to 
80,000 lbs. per square inch, an elastic limit of over 40,0C0 lbs., and an elong¬ 
ation in 8 inches of over 30 per cent. With 10 per cent of aluminum, the 
rolled bars have an ultimate tensile strength of 100,000 lbs. per square inch, 
an elastic limit of 60,000 lbs., and an elongation of 10 per cent in 8 inches. 
If further rolled, it hardens and strengthens to 130,000 lbs. tensile strength 
with 5 per cent elongation. The 5 to 7 per cent bronzes can be hammered, 
rolled, and forged at a red heat, and are very similar in every way to mild steel. 
They are almost absolutely non-corrosive. It hardens by cold working, but 
may be annealed by heating to a red heat and quenching in water. It has 
a modulus of elasticity of about 18,000,000, which is higher than that of the 
alloys of copper, zinc, and tin. 

On account of the excessive shrinkage of this alloy in hardening, it is 
necessary to provide a large sinking head in casting, and to so locate this as 
to supply to the cast form the necessary fluid metal to give a sound casting 
as it shrinks away in cooling. It should be cast in heated moulds. 

* These metals form a chemical union. This explains the remarkable and uniform 
strength of this combination. See a paper by Leonard Waldo in Trans Am. Soc. Merit. 
Engrs., vol. xvm. p. 437, and one by Alfred E. Hunt in Jour. Frank. Inst., Aug. and 
Sep. 1897. 




180 


THE MATERIALS OF CONSTRUCTION. 


149. Alloyed (or Hardened) Aluminum. —Just as a small percentage of 
'aluminum added to copper greatly hardens and strengthens it, without de¬ 
stroying its ductility, so a small percentage of copper added to aluminum 
works a similar change in this soft metal. If more than 15 or 20 per cent 
of either be added to 85 to 80 per cent of the other, however, the resulting 
mixtures become hard, weak, and brittle, and entirely worthless as commer¬ 
cial products. 

Both tin and zinc, up to 15 per cent, are used to harden and strengthen 
aluminum, while an alloy of 15 per cent zinc, 3 per cent tin, and 82 per 
cent aluminum is especially recommended. There are a number of secret 
mixtures of hardened aluminum, some of which are used for casting bicycle- 
frames. 

150. Aluminum in Steel. —If about one pound of aluminum per ton of 
steel be added to the heat just before drawing or teeming, it prevents the 
formation and escape of gases, and gives solid ingots or castings. For steel 
castings two to three pounds per ton is now commonly, added to the melted 
steel by throwing small pieces into the ladle as the steel is drawn from the 
furnace. In both methods it permeates the entire mass without artificial 
stirring, as manganese does, and seems to have very much the same effect. 
Its effect on cast iron are the same as those of silicon, but as it is much more 
expensive it is not used in this way. In steel, however, its use is common, 
as nothing seems to take its place. Besides preventing blow-holes it adds 
to the ductility of the product. 

151. Alloys which Fuse below the Boiling-point. —The following remark¬ 
able alloys, all of which fuse at very low temperatures, may be used as safety- 
plugs in automatic fire-spraying pipe-systems in mills and for similar pur¬ 
poses. 

TABLE XVII.—FUSIBLE ALLOYS. 


Name. 

Percentage of Ingredients. 

Fusing 

Tempera¬ 

ture. 

Bismuth. 

Lead. 

Tin. 

JCadmium. 

Newton’s. 

50 

31 

19 

0 

95° C. 

Bose’s. 

50 

28 

22 

0 

100° c. 

Darcet’s. 

50 

25 

25 . 

0 

93° C. 

Wood’s.'i. 

50 

24 

14 

12 

66-71° C. 

Lipoirtz’s. 

50 

27 

13 

10 

60° C. 




























CHAPTER XI. 


LIME, CEMENT, MORTAR, AND CONCRETE. 

LIME AND NATURAL CEMENT. 

152. Quick, or Fat, Lime.—If carbonate of lime (CaC0 3 ), as found in 
ordinary limestone, or marble, or chalk, be heated to a temperature of 
about 800° F., when it becomes a cherry-red, the carbon dioxide (C0 2 ) is 
driven off, and the oxide of calcium (CaO) remains, and is called quick¬ 
lime. In a pure carbonate of lime 44 parts by weight of carbon dioxide 
(carbonic acid) are combined with 56 parts by weight of oxide of calcium, 
or quicklime. Since the rock will contain some moisture, the amount of 
quicklime obtained from burning limestone will never be more than one 
half the weight of the stone charged. The calcium oxide., or quicklime, 
cannot be decomposed by heat, but it has a very strong affinity for water. 
When water is added to it, it rapidly rises in temperature, swells, and falls 
into an impalpable powder, and increases its volume to about three times 
its initial volume before the water was added. This process is called slack¬ 
ing, and the product is then called hydrated, or fat, lime (calcic hydrate), or 
slacked lime, or lime paste or putty when further diluted with water. The 
quicklime, or calcium oxide, will slack by absorbing moisture from the 
atmosphere, unless kept in closed vessels. It is therefore not kept in stock 
for any great length of time, as it becomes bulky and difficult to handle 
when slacked. It can be kept indefinitely without deterioration in the 
form of lime paste, or putty, if kept wet so as to exclude the air. Quick¬ 
lime is not found, as such, in nature, since it has a tendency to recombine 
with carbonic acid from the atmosphere, and form carbonate of lime. 
Rocks composed of nearly pure carbonate of lime are found in all parts of 
the world, and they have been used in this way for the manufacture of 
quicklime for mortar from the most ancient times. In slacking, 18 parts 
by weight of water unite with 56 parts by weight of quicklime, making 74 
parts of calcic hydrate, Ca(OH) 2 . The heat generated in slacking greatly 
facilitates the process, and some limes will slack in boiling water which 
cannot be slacked by the use of cold water. Limes of this latter class are 
called “ poor,” in distinction from those which slack readily, which are 
commonly termed “fat.” 

153. Hardening of Lime-mortar.—When quicklime has been slacked 

and mixed with sand it forms what is commonly called lime-mortar, which 

181 


182 


TEE MATERIALS OF CONSTRUCTION. 


is used for laying brick and stone masonry, for plastering houses, and 
the like, where the mortar-joints will be exposed to the action of the air 
only. Because of the great shrinkage of lime-paste in drying, it cannot be 
used neat, but must always be mixed with several times its volume of sand. 
When exposed to atmospheric action, the hydrated lime, Ca(OH) 2 , slowly 
unites with carbonic acid (C0 2 ), which is always present in the atmosphere, 
thus changing a portion of the hydrated lime back to its original form of 
carbonate of lime, leaving another portion in the hydrated form. Since the 
carbonic acid can have access to the lime only by the circulation of air 
through it, it follows that this chemical change occurs mostly at the outer 
and exposed surfaces of lime-mortar joints, and does not take effect at a 
distance from the surface to any appreciable extent, except through the 
lapse of long periods of time. In all cases, therefore, where it is neces¬ 
sary for the mortar to harden in a comparatively short time, lime-mortar 
must not be used. 

154. Hydraulic Lime.—When a limestone contains from 10 to 20 per 
cent of clayey matter, new combinations of lime and the silica in the clay 
are formed in the furnace, if the temperature is sufficiently high, which 
causes the product to slack less readily, and with a much less increase of 
volume, than in the case of quicklime. Hydraulic lime is partially slacked 
on drawing from the kiln by adding from 15 to 20 per cent of its weight of 
water, and it is then thrown into large heaps. The steam thus formed 
causes it to slack in the course of a week, after which it is screened and 
packed for market. It cannot be kept in the form of paste, as fat lime 
always is, as it would harden, like cement. If this same rock be calcined at 
a high heat and reduced to a clinker but not fused, and then ground with¬ 
out slacking, it forms the natural cement described in the next article. It 
is changed from the one product to the other by the chemical reactions 
which occur at the higher temperature in the kiln. Mortar made with this 
lime will harden somewhat under water, by a process of partial crystalliza¬ 
tion, and hence it is called hydraulic lime. Limestones having a composi¬ 
tion suitable to make hydraulic lime are very common in England and 
Europe, but are not common in America; hence what is there known as 
hydraulic lime is not known in America as an article of commerce. 

155. Natural Cement.—Carbonate and magnesian limestone rocks con¬ 
taining from 20 to 40 per cent of clay, when calcined to a clinker, just 
short of fusion, and finely ground, give a product which sets or hardens 
quickly on the addition of about 25 per cent of its weight of water, without 
any increase of volume, and forms a permanent artificial stone which in¬ 
creases. in strength and hardness for many years. This product is known 
as natural cement ,* because it is produced wholly from a natural rock. It 


* In England and on the Continent this kind of cement is commonly called Roman 
cement, from a supposed similarity to the cement the Romans used on their hydraulic 






LIME, CEMENT, MORTAR, AND CONCRETE. 


183 


has become customary to give to natural cements local geographical names, 
indicating the place of their manufacture. This is more especially appro¬ 
priate since the natural cements made in a given locality will have the 
same general characteristics, because they are all made from the same sedi¬ 
mentary rock. These cements are very largely used in America, some of the 
principal varieties being the “Rosendale” cement, made near the Hudson 
River in Ulster County, N. Y., the “Utica” cement, made at Utica, Ill., 
the “Louisville” cement, made mostly on the Indiana side of the Ohio 
River in the vicinity of Louisville, Ky., and the “ Milwaukee” cement, 
made at Milwaukee, Wis. Such cements are made at various other places 
in the United States and Canada, and are known by their corresponding 
local geographical names. These cements are now very cheap, and often¬ 
times are found to vary greatly in quality. While the better grades of 
natural cement are quite sufficient in strength for nearly all kinds of 
engineering works, the want of uniformity in their hardening properties 
is a serious objection to their use. 

Some of the American natural cements are very quick setting, which is 
a further objection to them, since it is difficult to use the mortar or concrete 
made from them before it begins to set, or harden. 

The old Roman cement used by the Romans in their hydraulic masonry 
constructions was made by mixing volcanic ashes with lime in proper pro¬ 
portions. 

PORTLAND CEMENT. 

156. Historical. —An artificial mixture of lime and clay in proper propor¬ 
tions, calcined to a clinker at a temperature of incipient fusion, and finely 
ground, is called Portland cement. It received this name in 1824 in Eng¬ 
land, where it was first made, from its similarity in appearance when 
hardened to the noted oolitic limestone from the “ Isle of Portland”* * long 
used in England for building purposes. It was patented in that year by 
Mr. Joseph Aspdin, a Leeds brickmaker, as an “artificial stone.” He 
mixed pulverized limestone, taken from the public macadamized roads, 
with clay, by adding water enough to reduce it to a liquid form. This was 
then dried and burned “in a furnace similar to a lime-kiln till the car¬ 
bonic acid is entirely expelled.” The necessity of burning to a clinker 
was not given in the specification, and was probably not known at that 
time, neither was the proper proportion of clay mentioned. His success was 
therefore something of an accident, as was doubtless the discovery of the 

engineering works. There are few suitable rocks in Europe for making this cement. It 
is extremely irregular in composition, and not to be compared with the very uniform 
beds found in inexhaustible quantities in the United States. If such natural cement 
rocks as we have, bad been common in England and on the Continent, it is almost certain 
that the artificial Portland cement would never have been discovered. 

* This is really a peninsula on the south coast of England, in Dorset, near Weymoutb, 
noted for its building-stone. The Westminster cathedral is built of this stone. 




184 


THE MATERIALS OF CONSTRUCTION. 


hydraulic property of the mixture itself. Aspdin began manufacturing his 
cement at Wakefield * * * § in 1825. 

Previous to his time a kind of natural cement had become common 
under the general name of “Roman cement/’ This was made by calcining 
nodules (geodes) of a clayey limestone found along the seacoast, “at a heat 
nearly sufficient to vitrify them/’ and grinding the product. (Patented by 
James Parker in England in 179G.) 

The discovery that the hydraulic property of certain limes was due to 
the clay ingredient is due to Smeaton (about 175G), who had some knowl¬ 
edge of chemistry.f The occasion of these investigations was the building 
of the third Eddystone lighthouse. This, therefore, marks the beginning 
of all intelligent study of the subject of hydraulic cements.]; 

Although Aspdin began manufacturing Portland cement in the north 
of England in 1825 (and continued to 1853), and it was introduced exten¬ 
sively on the Continent, it was not known in London till made by J. M. 
Maude and Son (with Aspdin’s son) in 1843 under Aspdin’s patents in what 
is now a part of London, and by J. B. White and Sons, in Kent, in 1845. § 

In tests made in 1843 for the new Houses of Parliament this Portland 
cement was shown to be superior to the Roman cement then in common 
use, but engineers and architects were slow to grant the fact. Public com¬ 
petitive tests between the above-named firms were conducted in 1848 
which further proved the superiority of the Portland cement, || and after 
the Exhibition in 1851, at which many tests were made, its use soon became 
general in England. 

Many failures marked the first thirty years of the Portland-cement 
manufacture, from an entire neglect of the chemical analysis of the ingredi¬ 
ents. Reliance was placed solely on the empirical knowledge of workmen 
ignorant of chemical science, and much sophistry and deception were used 
to cover up their failures. It is now known that good Portland cement 


* A small city in Yorkshire near Leeds. 

f A report of his investigations and conclusions was not published till 1791, in Book 
III of his Narrative of the Building, etc., of the Eddystone Lighthouse. 

x For a very good account of the early history of this subject see Redgrave’s Cal¬ 
careous Cements, London, 1895. 

§ This was a Roman cement factory, but Mr. I. C. Johnson, their manager, after 
long search and experimentation, the Aspdin processes being secret and purposely mys¬ 
tified, discovered the secret of burning to a clinker. He also at last discovered the 
proper proportions. From an account by Mr. Johnson himself in The Building News 
(London), 1880. 

|| These tests consisted in building out brick beams from solid walls, and in crushing- 
tests of large cement prisms. As late as 1845-6 Sir Robert Peel announced in Parlia¬ 
ment his intention of taxing the use of the clay nodules of which the Roman cement was 
then made, to prevent their complete exhaustion, and to retain sufficient of them for 
government works. Aspdin thereupon addressed him a personal note describing his 
artificial cement, and the proposed measure was dropped. 




LIME, CEMENT, MORTAR, AND CONCRETE . 


185 


can be made anywhere by properly combining, burning, and grinding a 
mixture of carbonate of lime and a suitable clay, the only elements of 
commercial success being economy and scientific direction. 

Since a good Portland cement, with or without sand, gravel, and broken, 
stone, makes an artificial compound equal to almost any natural stone in 
hardness, strength, and durability, and since it can be moulded to any form 
and is much cheaper than quarried and cut stone, it is constantly finding 
wider and wider fields of application. This material has already worked a 
revolution in engineering construction nearly equal in significance to that 
following upon the general use of the Bessemer and open-hearth processes 
of making steel. The character of Portland cement also has constantly 
improved, until now it has reached practical perfection. Within the past 
ten years the improvement has been very marked, as a result of the universal 
system of testing now in vogue, and of the general employment of compe¬ 
tent scientific supervision of the works, made necessary by these tests on 
the part of the user. Portland cement is now made on a gigantic scale in 
Germany, Belgium, France, and England, and its manufacture is rapidly 
increasing in the United States. 

157. The Ingredients of Portland Cement.—All mixtures, natural or 
artificial, of carbonate of lime (CaC0 3 ) and clay in the proportions of from 
72 to 77 per cent of the former to 20 to 25 per cent of the latter will, when 
calcined at the proper temperature, produce a Portland cement of fair 
quality. After calcining, and driving the carbonic acid (C0 2 ) from the 
carbonate of lime (CaC0 3 ), the proportions of lime (CaO) and clay (silicate 
of alumina (A1 2 0 3 , 2Si0 2 , 2H 2 0) are about 60 to 65 per cent of lime and 
from 25 to 30 per cent of clay, with some 5 per cent of other ingredients, 
such as sulphate of lime, magnesia, iron oxides, etc. “A variation in the 
lime ingredient of one per cent above the true amount will give a cement 
liable to crack on long exposure to water, and a deficiency of one per cent 
of lime will reduce the strength of the cement and also make the mixture 
liable to fuse in the kiln.” * The most competent chemical supervision and 
continual analyses of the ingredients are therefore necessary to secure the 
best results. 

158. Chemical Characteristics cf the Ingredients.—The carbonate of 
lime should be nearly free from all other substances except clay (silica 
and alumina). While magnesia in small amounts is not injurious, it is 
probably inert, and the sulphur compounds are a positive injury, above a 
two or three per cent limit. The iron acts as a necessary flux. 

159. The Clay.—“ The best clays for the cement-manufacturer are those 
having a greasy, unctuous feeling, quite smooth to the touch. As a rule, 
clays which stain the fingers should be avoided, as being either too much 

* Prof Spencer B. Newberry in the Engineering Magazine, June, 1894. Mr. New¬ 
berry is chemist and manager of the Sandusky, O., Portland Cement Works. 





186 


THE MATERIALS OF CONSTRUCTION. 


impregnated with iron compounds, or containing a large proportion of 
organic or other impurities. This does not hold good in the case of the 
carboniferous shales, some of which are rich in matters which assist in the 
calcination of the cement. Shales which contain much alum, selenite, or 
iron pyrites, and many of the shales having a high percentage of carbonate 
of lime, need great care in manipulation, as they are apt to fluctuate widely 
in composition and to lead to mistakes in the proportions of the ingredients. 
Some clays contain a high percentage of sandy particles, or of nearly pure 
silica not in combination with lime, iron, or alumina, and these clays, though 
useful to the brick-maker, are ill adapted for cement-making. They are 
generally characterized by a harsh gritty touch when tested between the 
finger and thumb, and it is possible to wash out a considerable percentage 
of sandy particles/’* 

160. Silica and its Compounds.—“ It will be necessary, in order to 
understand the chemistry of cements, to treat in some detail of silica and 
its compounds. Silica, the oxide of the element silicon, is found very 
widely distributed in nature, sometimes pure, but more often in combina¬ 
tion with other substances, as it has a great tendency to form complex 
salts, known as silicates. It plays the part of an acid, and combines with 
lime, alumina, iron, and the alkalies in a vast number of different propor¬ 
tions. It is found that 28 parts by weight of silicon and 32 parts by weight 
of oxygen are present in silicic anhydride or silica, having the chemical 
formula Si0 2 . Clay, a hydrous silicate of alumina, may oe taken as a type 
of the silica compounds, while quartz, flint, and chalcedony consist of 
almost pure silica. Porcelain clay, which contains about 47 per cent of 
silica, 39.2 per cent of alumina (A1 2 0 3 ), and 13.7 per cent of water, and 
corresponds to the chemical formula Al 2 0 3 2Si0 2 -f- 2H 2 0, or clay proper, 
with a molecular weight of 258.4, may represent the silicates. There are, 
however, an enormous number of clays in which silica and alumina are 
present in very varying proportions, and which contain in addition iron, 
alkaline matters, lime, etc. For certain of these clavs it becomes almost 
impossible to propound any reliable chemical formula to express their 
composition; and alumina, while it may combine in certain definite pro¬ 
portions with the silica as a base, is also capable of acting as an acid, and of 
combining with lime and the alkalies, especially at high temperatures, to ^ 
form certain more or less unstable and little known compounds termed 
aluminates.” * 

161. Alumina is the oxide of the metal aluminum which has the atomic 
weight of 27.2, and two parts of aluminum combine with three parts of oxy¬ 
gen, equal 48, to form its only known oxide, termed alumina, amounting in 
all to 102.4. It will not be necessary to study in detail the combinations of 
silica and alumina with iron and the alkalies—soda and potash—though 
these compounds play a very important part in cement action.” * 


* Redgrave. 






LIME, CEMENT , MOUTAlt, AND CONCRETE. 


187 


162. Sulphur and its Compounds. 

Portland cement may be associated 
with a small percentage of gypsum 
or sulphate of lime (calcic sulphate 
CaS0 4 , 2II 2 0), the water of which is 
driven off in the calcining process, 
reducing this compound to what is 
commonly known as plaster of paris 
(CaSOJ. Sulphur may also be intro¬ 
duced in the fuel used for burning, 
or from the clay which sometimes 
contains iron pyrites. The sulphuric 
acid relieved from these compounds 
may unite with the free lime in the 


—The carbonate of lime used for makin 


cr 


soo 


400 


300 


d 





>> 



0/ 

(I 






.j 

w 

/ 0 

f 







fj 







ik 








K 

§ 









J A 







L * 

m 

vm. 

'40£ . 


'//m 




300 


/OO 


_ 

i 


&Y 4GL 

- sfJR/A. 

tffofAro 
■ OF 

5?J 

N / 

taO\ 


1 

A 

k 

V 

3/73YJ 


* 

\ 

\ 

33303/VT/Il 

1_ 

1 


■0 A /0 

Fm. 78.—Effect of Plaster of Paris on 
Time of Setting of Cement. (Wheeler, 
Rep. C/if. Engrs. 1895, p. 2938.) 


0 /.0 2.0 3.0 

Fig. 79. —Showing the Effect of Plaster of 
Paris on the Strength of Portland-cement 
Mortar, 1 C. : 3 S. (Tetmajer, vol. vii. p 
39.) 


furnace and form an additional portion of calcic sulphate. The effect of 
this calcic sulphate or piaster of paris in quantities not exceeding two or 
three per cent is to greatly delay the time of setting (Fig. 78), but to 
increase slightly the final strength of the cement (Fig. 79). When present 
in quantities exceeding four or five per cent both these effects are lost, and 
it is also considered injurious in other ways, since it is comparatively sol¬ 
uble in water, and when present in the kiln in considerable quantity it 
leads to the formation of calcic sulphide, which decomposes the iron com¬ 
pounds in the cement, thus leading to disintegration. The German standard 
rules allow a proportion of calcic sulphate not to exceed two per cent, but an 
effort has recently been made to have this limit raised to three per cent. 

163. The Chemical Reactions Produced in Calcining. —Professor Spencer B. 
Newberry has proved* by the most elaborate synthetical analysis ever made on 

* In a paper read before the New York section of the Society of Chemical Industry, 
October, 1897, and printed in Cement and Engineering News, 1897-8. 













































188 


TIIE MATERIALS OF CONSTRUCTION. 


Portland cement that the proper chemical combinations which should be effected in 
the furnace are : 

Proportions by Weight. 


Tri-silicate of Lime (3Ca0,Si0 2 ).. . 
Di-aluminate of lime (2Ca0,AL0 3 ) 


S Lime, 

CaO, 

28 

1 Silica, 

SiO*, 

10 

\ Lime, 

CaO, 

11 

1 Alumina, ALO3, 

10 


Hence we may have the following rule for the maximum lime ingredient: 

Multiply the percentage of silica by 2.8 and the percentage of alumina by 1.1; 
add the products; the sum will be the number of parts of lime required for 100 
parts,of clay. 

Since 2.8 parts of lime correspond to 5.0 parts carbonate of lime, and 1.1 parts 
lime correspond to 2.0 parts carbonate of lime, the rule may be stated as follows: 

Five times the percentage of silica plus twice the percentage of alumina equals 
the number of pjarts of carbonate of lime required for 100 parts of clay. 

Magnesia probably remains inert, and does not combine with alumina and silica. 



Fro. 80.—Showing the Inferior Character of the Furnace-dust compared with the 
Ground Clinker, when used in Mortar, 1 C. : 3 S. (Tetmajer, vol. vii. p. 12.) 

It is harmless if not forming over five or six per cent of the whole.* Oxide of iron 
is useful as a flux. 

The normal composition of some of the standard brands of Portland cement is 
given below. They all very closely agree with the rule given above for the lime in¬ 
gredient, the percentage of lime actually employed being slightly less than the rule 
gives, this being for the maximum lime ingredient. Since any imperfection of mix¬ 
ing before burning would result in free lime in the product if the full theoretical 
amount were used, it is best to fall a little short of this percentage in practice. 



Dykerhoff. 

(German) 

Germania. 

(German) 

Porta. 

(German) 

Empire. 

(American) 

Saylor’s. 

(American) 

Sandusky. 

(American) 

Lime, CaO. 

63.75 

66.04 

62.28 

64.00 

62.79 

64.19 

Silica, SiO a . 

19.35 

21.14 

22.69 

20.80 

20.64 

23.20 

Alumina, A1 2 0 3 . 

7.00 

6.30 

7.30 

7.39 

6.93 

7.03 

Iron oxide. Fe 2 0 3 .. 

4.50 

2.50 

2.87 

2.61 

5.41 

2.41 

Magnesia, MgO. 

Not det. 

1.11 

1.08 

Not det. 

1.72 

0 97 


Chatelier’s formulae are 


_ Ca0 + M S° > O and CaO + MgO 

SiO, - AUO, - Fe 2 0 3 - a u SiO s + A1 2 0 3 - 


* The German Cement Manufacturers’ Association has allowed five per cent, since 1893. 
\ See Cement and Engineering News , Feb. 1898. The second of these formulae has 

























































LIME, CEMENT, MORTAR , ANI) CONCRETE. 189 

For methods of making commercial analyses of Portland cements see 
Appendix E. 

Since there is no further mixing of the lime and clay ingredients in the furnace 
in the calcining action, it is absolutely necessary, in order to secure perfect results, 
to have the lime and the clay perfectly and uniformly mixed before going into the 
furnace; that is to say, each particle of lime should have adjacent to it its particle 
of clay with which to unite when the proper temperature has been attained. Since 
it is, of course, impossible to intermix these materials to this degree of perfection, 
there must of necessity result from the burning more or less inert or uncombined 
clay and lime without cementing qualities, which inert matter forms a large part of 
the furnace-dust. (See Fig. 80.) If the ingredients were actually fused or melted 
into a liquid mass, and the chemical action were to take place after the ingredients 
were in the liquid form, a much more perfect union of the elements would of course 
be effected. In the formation of the clinker which is ground into Portland cement, 
however, the ingredients are not fused, since fusion would be fatal, and hence the 
elements of the mixture are incapable of uniting except they be in immediate juxta¬ 
position. The further improvement of Portland cement evidently lies in the direc¬ 
tion of more perfect and more uniform mixture of the raw materials in a finely 
divided state before they are burned. From experimental tests which have been 
made in this direction, it would seem that the strength of Portland cement might 
be made at least twice what it is now, by more perfectly satisfying this require¬ 
ment. 

164. The Chemical and Physical Changes involved in Setting and 
Hardening. —By the setting of cement is meant its initial change from a soft 
or plastic mortar to a friable solid. This change is usually effected with 
great suddenness, after it begins, as shown by the curves in Fig. 333, and 
it has been shown to be always accompanied by the evolution of heat. 
After the cement has become thoroughly set it still is very weak, and is 
readily pulverized in the fingers. If left undisturbed, however, it increases 
in hardness and strength, sometimes for several months, but generally for 
many years. There is no relation between the time elapsing after wetting 
before setting takes place, and the period of time required to attain to 
nearly its ultimate strength. The setting of cement is thought to he effected 
hi) the crystallizing out of the silicate and the aluminate of lime, which 
are soluble in water in their anhydrous form. After dissolving in the 
water they pass to the hydrated state in which they are insoluble, and hence 
are precipitated in a crystalline form, with a development of heat. This 
process is greatly hastened at higher temperatures. 

The hardening of cement is due to a continued crystallization of salts 
from solution, and to further chemical and physical changes which develop 
slowly, but which continue for long periods of time. M. Fremy regards the 
aluminate of lime as the chief source of the hardening property, and he also 
thinks the silica and the alumina of the clay are separated by calcining and 
take on allotropic forms, ready to unite into new compounds with the quick¬ 
lime when water is added. There are so many kinds of combinations of 
various substances which will serve to produce the final characteristics of 


usually been given erroneously in America, Laving been wrongly printed in Chatelier’s 
paper before the World’s Eng. Congr., 1893. 




190 


THE MATERIALS OF CONSTRUCTION. 


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hardened Portland cement, that there must be many different chemical 
compounds which, after calcining, will harden on the addition of water. 

The problem is so complicated 
that it has as Tr et defied a complete 
chemical analysis. 

165. Slag-cements.—Many va¬ 
rieties of iron blast-furnace slags 
will make an excellent cement 
when ground with hydrated or 
slacked lime, without further cal¬ 
cining. The slag is “ granulated ” 
by running it from the blast-fur¬ 
nace into water, where it forms into 
a brittle, porous, pumice-like mass 
resembling caked sand, and in this 
condition it is called “ slag-sand.” 
It is now easily crushed into 
powder, but retains the water in 
its meshes so that it is very diffi¬ 
cult to dry it. Sometimes this 
“ slag-sand 99 is calcined at a low 
heat simply to dry it. 

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ing the melted vitreous slag in 
water has an effect upon it further 
than to simply reduce it to the 
porous, friable condition, since 
when allowed to cool in the ordi¬ 
nary way, into a solid mass, and 
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added, it has no hydraulic proper¬ 
ties (see Fig. 81). It seems prob¬ 
able, therefore, that the sudden 
cooling leaves the chemical com¬ 
pounds in a more unstable con¬ 
dition, so that when powdered 
and intimately mixed with hy¬ 
drated lime, and water added, 
they are ready to enter into new 
chemical combinations with the lime. To three parts by weight of the 
dry “slag-sand” is added one part of hydrated lime (CaH 2 0 2 ), and these 
are thoroughly ground together and intermixed by suitable mechanical 
appliances. This cement does not deteriorate appreciably by lapse of 
time. 


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LIME, CEMENT, MORTAR, AND CONCRETE. 


191 


While the exact chemical reactions have not yet been determined for 
slag-cements, it seems certain that the hardening of slag-cements consists of 
a gradual action of an active form of silica on the free lime, as in the case 
of puzzuolana or trass. To make the silica hydraulically active it must 
apparently be calcined with a certain amount of basic material, as lime or 
alkali. 

Slag-cements make a more unctuous mortar and are much liked by 
architects for laying brick walls and piers, and for making floors, sidewalks, 
etc. It is slow setting and does not stain the masonry in outside walls. It 
is often mixed with additional amounts of lime-putty to further delay the 
time of setting, or to cheapen the mortar, or to make it work smoother 
under the trowel, but it does not resist air exposure well. 

166. Sources of the Raw Materials Used in Making Portland Cement.*— 
“ Portland cement is made from carbonate of lime and clay. These materials 
may be naturally mixed, as in the case of argillaceous limestones, or entirely 
separate. In all cases, however, it is necessary to bring the material to cor¬ 
rect composition by artificial additions and thorough mixing. In England 
chalk is the form of carbonate of lime employed. In Germany the chief 
material is marl (mergel), by which is understood a more or less hard lime¬ 
stone rock containing clay. In some German factories a pure soft marl 
(weisenkalk), or fresh-water chalk, is used, consisting chiefly of carbonate 
of lime and similar to the marl deposits of this country. 

“In the United States the materials used are very similar to those of 
Germany. Most of our clay limestones are highly magnesian, and there¬ 
fore unsuitable for Portland cement, though they are used on an immense 
scale for natural-rock cements. At certain localities, however, as in Lehigh 
County, Pa., at Phillipsburg, N. J., and in the far West, limestones con¬ 
taining sufficient clay and nearly free from magnesia are abundantly found, 
and in the above localities and from this material most of our Portland 
cemeni is made. In the Lehigh County region, the chief seat of the 
American Portland-cement industry, the different strata of rock are care¬ 
fully selected and mixed in such proportions as to give a material of the 
right composition. 

“ In central New York, in Michigan, in Ohio, and in Indiana large 
deposits of pure white marl are found. This is generally called ‘shell- 
marl/ and was supposed to result from the disintegration of fresh-water 
shells. In the opinion of the writer, however, these marl-beds are generally 
pulverulent deposits from calcareous springs, and are not formed from 
shells to any great extent. At the localities above mentioned this material, 
artificially mixed with clay, is largely used for the manufacture of Portland 
cement. Owing to the soft, fine-grained character of the marl, the mixing 
can be much more cheaply done than in the case of limestone, though this 

* This and the following article are taken from the paper on Portland Cement by 
Prof. Spencer B. Newberry, in the U. S. Geol. Surv. Report for 1894, Part IV, p. 581. 





192 


THE MATERIALS OF CONSTRUCTION . 


advantage is largely compensated for by the necessity of drying out the 40 
to 50 per cent of water which the marl generally contains. It must be 
remembered also that in the argillaceous limestones the ingredients are 
already uniformly mixed in nearly the proper proportions, while with the 
pure lime and clay this mixing must be wholly effected by artificial means. 
The leaving of any free lime in the final product, from imperfect mixing, 
has often led to the disintegration of the mortar by sea-water, and by fresh 
water containing carbonic acid in solution. 

“As already stated, most American Portland cement is made from argil¬ 
laceous limestone, as shown by the following table. 

-NUMBER OF AMERICAN CEMENT FACTORIES USING LIMESTONE COMPARED 

WITH THE USERS OF MARL (1897). 


Factories Using 

Number. 

'Quantity. 

Limestone. 

18 

Barrels. 

2,282,126 

895,649 

Marl. 

11 


Total. 

29 

2,677,775 



The argillaceous limestone factories are mostly located in the region of 
Lehigh County, Pennsylvania, while the marl factories are mostly in New 
York, Ohio, Michigan, and Indiana. Factories using chalk have been 
established in Arkansas. 

167. Processes Used in Pulverizing and Mixing the Raw Materials.— 

There are, in general, three processes employed in preparing this intimate 
mixture of the raw materials, which may be designated “ The Wet Process,” 
“ The Semi-wet Process,” and “ The Dry Process.” 

1. The Wet Process was originally employed in England and in France, 
and was used for tlie admixture of crushed chalk and clay. These were 
pulverized and mixed in “ wash-mills ” with such an excess of water as to 
form a thin liquid. 1 his was stirred by such an arrangement as that shown 
in Fig. 82, the escape being at the top over a lip or weir. The coarsest 
particles settled in this wash-mill, and such granulated matter as escaped 
in the liquid was intercepted on its way to the “ backs,” which were open 
tanks some foui feet deep, with earth or gravel bottoms. The mixture was 
now allowed to settle for some days, when the clear water was siphoned off 
and the “ slurry” left to dry in the open air until it could be handled with 
a shovel. It was then wheeled upon drying-floors and dried by artificial 
heat into irregular clods or masses, when it was sent to the furnace. Even 
in summer this process required many weeks’ time for its completion, and 
in the first settlement the chalk and clay ingredients would sometimes have 
a different specific gravity, and hence they would not settle simultaneously. 
This would give an uneven mixture, which would be so far fatal, since it 
















LIME, CEMENT, MORTAR, AND CONCRETE. 


193 


could not be corrected. This process is going out of use even for such 
material as is suited for this method of treatment. 

2. The Semi-wet Process consists in mixing the ingredients in the state 
of a soft paste. This may be done either by grinding them together in this 
condition or by means of "edge-runners.” These consist of heavy cast-iron 
cylinders of short length, mounted on a horizontal axle which is made to 



Fig. 82.—Wash-mill used in the Wet Process of making Portland Cement. 

swing about a vertical axis, thus causing the heavy cylinder to roll about on 
a bed-plate. Sometimes the roller-axle maintains a fixed position and the 
plate revolves on which it rests. This is an efficient pulverizer and mixer 
when the ingredients are comparatively soft. It does not produce as 
uniform a pulverization, however, as a grinding-mill. Both these processes 
are used in America.* 

3. The Dry Process is used in Germany, and in Pennsylvania and New 
Jersey in this country, where the materials consist of argillaceous lime¬ 
stone having nearly the proper composition for making Portland cement. 
The rock is first crushed and then ground. The final mixture of limestone 
and clay-shale is made before the material is ground, so that the process of 
grinding effects a very thorough mixing. The ingredients must be reduced 
to an impalpable powder in order to make possible that thorough mixing 
necessary to enable each molecule of lime to associate itself with its mole¬ 
cule of clay in the calcining process, so as to produce the true chemical 
combinations in the clinker. If the limestone used has primarily nearly 
the composition required, which is sometimes the case in America, then it 
is evident that any want of perfection in the first grinding and mixing of 
the raw materials is not so injurious, since the native mixture is not only 

* At Bellefontaine, O., the “ edge-ruuners ” are used, and at Sandusky, 0., the 
grinding-mill, the material in both cases being a soft marl and clay. 



































































































194 


TILE MATERIALS OF CONSTRUCTION. 


nearly correct as to proportions, but so far as it goes the admixture is prac¬ 
tically perfect. When pure carbonate of lime is used (as in the case of soft 
marl) with clay, there is no primary mixture of the lime and clay at all, and 
hence the necessity of a much more elaborate artificial mixing process than 
when these ingredients are found intimately associated in a natural rock 
and to nearly the correct proportions. On the other hand, the soft marl 
and clay (of Ohio, for instance) are much more easily worked than the hard 
limestone and clay shales (of Pennsylvania). In order to enable the hard 
materials to compete successfully with the soft, it is necessary that the 
limestone should contain primarily nearly the proper proportion of clay. 

After the dry grinding and mixing of the raw materials, the dust is wet 
sufficiently and moulded into bricks (thus obtaining a further mixing), and 
then dried and burned. The raw powder cannot be calcined in the ordinary 
furnaces without first compacting it in aggregate forms to allow of a draft 
of air through them. In the tubular rotating furnaces it is calcined as a 
dry powder, and this is one of the great advantages of that process. 

168. Processes Used in Burning Portland Cement.—“ There are three 
distinct forms of kiln used in burning Portland cement in America. These 
are (1) intermittent or dome kiln, (2) continuous kiln, of the Dietzsch or 
Shofer type, (3) rotary furnace. In the old-fashioned intermittent kiln the 
bricks of cement mixture are charged into the kiln with coke in alternate 
layers, and the whole allowed to burn out and cool down before emptying. 
The Dietzsch or Shofer continuous kiln is eontinuouslv charged with bricks 
of cement mixture and soft coal, and the burned clinker periodically with¬ 
drawn at the bottom. It presents the great advantage of cheaper fuel and 
economy of labor, and burns the dry powdered material. The rotary fur¬ 
nace consists of a rotary cylinder heated by a blast of air and gaseous fuel, 
the material being continuously run in at one end, and issuing as burned 
clinker at the other. This process was patented by Mr. Frederick Itansome, 
in England, in 1885, and has been subsequently modified and improved by 
others. Many difficulties have been met with in carrying out this plan, but 
it is now successfully operated at a number of works in this country. It 
would seem to be the most rational method of carrying on the burning of 
cement, since it effects an enormous saving in time and labor, and allows, 
the temperature to be regulated far more exactly than is possible in the 
older processes. Crude or fuel oil is used as a source of heat at all points in 
America where this kiln is employed, though producer-gas with or without 
regenerative furnaces might be employed.* 

“ In the United States most of the Portland cement produced is burned in 
the old-fashioned intermittent kilns. The Dietzsch kiln is used at Harper 
and Middle Branch, Ohio. The Shofer kiln is to be used at new works now 

* This process requires a much greater fuel expense than the kilns and seems to be 
used only where the raw material will not adhere sufficiently by wetting to form, 
briquettes which can be burned in kilns.—J. B. J. 





LIME, CEMENT, MORTAR, AND CONCRETE. 


195 


beginning operations at Glens Falls, N. Y. The rotary furnace is in oper¬ 
ation at Colton, Cal., Phillipsburg, N. J., Coplay, Pa., Sandusky, 0., and 
Bronson, Midi. The following table shows the number of barrels of cement 
made during the year 1897 in vertical kilns (continuous and intermittent) 
and the rotary furnace. 

AMOUNT OF PORTLAND CEMENT MADE IN KILNS OF VARIOUS KINDS 


IN THE UNITED STATES IN 1897. 

Barrels. 

Rotary furnace, eight factories. 1,311,319 

Vertical kilns (continuous and intermittent), twenty-two factories. 1,366,456 

Total. 2,677,775 


It thus appears that the output of rotary furnaces has increased much 
more rapidly than that of vertical kilns. The recent rapid advance in the 
price of crude oil is a great obstacle to the use of the rotary furnace. At¬ 
tempts are being made to substitute producer-gas for crude oil in burning 
cement. There is no reason why this should not be successfully done, and 
the change will greatly reduce the cost of 
burning cement at all points where the 
rotary process is used.” 

169. Grinding the Clinker. — “ For 
grinding the finished product the Griffin 
steel mill is used at the larger factories. 

Some of the older works still use buhr- 
stones. The Griffin mill* consists of a 
steel ring, against the inside surface of 
which a heavy steel roll revolving on a ver¬ 
tical shaft presses by centrifugal force • 

Fig. 83. The mill is provided with screens 
which allow powder of the requisite fine¬ 
ness to pass through, while the coarser 
particles drop back into the mill. This 
mill is an American invention, and is 
rapidly finding its way into the leading 
cement-works of Germany.” 

* Made by the Bradley Pulverizer Co., Boston, Mass. It is used for all kinds of 
pulverizing where buhrstones and stamp-mills have hitherto been employed. It works 
in either wet or dry material, and is an extremely ingenious and successful grinding 
machine.—J. B. J. 



Fig. 83. —Perspective View of the 
Griffin Mill. 
























































































CHAPTER XII. 


THE MANUFACTURE OF VITRIFIED PAVING-BRICK. 

By H. A. Wheeler, E.M.* 

170. Definition.—As there is a lack of harmony in the use of the term 
vitrified brick, it is necessary to define what is meant by vitrified. There 
is a popular idea that a vitrified brick must be glassy, in accordance with 
the etymology of the word; whereas a truly glassy brick is impracticable to 
make—at least to a reasonably large percentage; and unless annealed with 
very much more care than is now given to paving-brick, such a brick would 
be too brittle for paving purposes, besides being badly misshapen. It is true 
that samples of excellent paving-brick frequently exhibit to an eminent 
degree a glassy or vitreous surface; but these vitreous faces are due to air- 
checks (caused by the hot brick being struck by cold air), and if the brick 
is broken along an unchecked or solid face it will not exhibit a glassy 
surface: it will there present a very close, dense, homogeneous, stone-like 
fracture, and this fracture is what is recognized and accepted as character¬ 
istic of a vitrified brick. There is a total absence of the individual parti¬ 
cles of the clay in such a fracture the presence of which characterizes build¬ 
ing and fire-brick. Furthermore, such a vitrified brick has a hardness of 6.5 
to 7, on Moll’s scale of hardness, or is about as hard as quartz (the hardest 
mineral in granite), and it readily scratches glass or the hardest steel. While 
this typical vitrified fracture is easily recognized by the experienced eve, 
there is no sharp line of demarcation between it and the glassy fracture 
on the one side (when the brick is overburned), and a hard but unvitrified 
brick on the other hand (when underburned)’, for clay gradually passes 
through a transition, when highly heated, from (1) an eminently porous, 
strong, and, rather hard condition just previous to the vitrifying-point; (2) 
to a very much harder, tougher, slightly porous condition when vitrified; 
and finally (3) to a very dense, glassy, non-porous condition when com¬ 
pletely vitrified, in which latter condition it is very apt to be decidedly brit¬ 
tle. These three stages of burning can usually be found in every kiln of 
paving-brick, with all intermediate transitions from one extreme to the other. 

* Formerly Assistant Geologist Missouri State Geological Survey, in charge of inves¬ 
tigations made on clays, and now (1896) manufacturing paving-brick in St, Louis, Dio. 

196 









THE MANUFACTURE OF VITRIFIED PAVING-BRICK 197 

though from CO $ to 90$ usually come within the second or properly vitrified 
stage. 

171. Clays employed for Paving-brick.— Three radically different classes 
of clays are employed in the manufacture of paving-brick, viz.: 

I. Surface Clays; 

II. Inferior Fire-clays; 

III. Shales. 

Surface Clays. 

By surface clays are meant those soft, unconsolidated clays at or near 
the surface which have been deposited during or since the glacial period, 
or that have resulted from the atmospheric decay of the underlying rocks. 
This class of clays was more frequently used in the earlier development 
of the paving-brick industry, but they have been almost completely 
given up on account of the great difficulty in successfully vitrifying 
a large percentage of the brick; for, as a rule, they are apt to be so very 
siliceous (or have from 60$ to 80$ silica), or else so very calcareous (or 
have from 10$ to 25$ lime), that there is usually a very narrow range of 
temperature at which they can be vitrified. Hence the brick are apt to be 
either too soft (underburned), or else overburned and badly misshapen, so 
that these clays have been generally abandoned for the safer-burning shales 
and fire-clays. 

Inferior Fire-clays. 

The inferior or impure fire-clays, which are frequently known in the 
trade as “ bastard fire-clay ” or “ pipe-clay,” have been quite largely used in 
the past, and are still employed to some extent in the manufacture of 
paving-brick. They are a class of fire-clays that contain sufficient fluxing 
impurities to enable them to be slightly vitrified, and the more impure 
the fire-clay the more successfully it can be used for this purpose. When 
the physical properties of the fire-clay are suitable, these impure fire-clays 
make an excellent quality of fire-brick, though they always show rather 
high absorption, or from 2$ to 5$ of water after soaking 24 hours in water. 
They never show a glassy fracture, and are rarely misshapen or kiln-marked, 
as in the other two classes of clays; but they are very much more apt to be 
soft, and therefore short-lived, from underburning, as it requires a very high 
heat to vitrify them. When properly vitrified, they make a very satisfac¬ 
tory paving-brick, on account of their toughness, and some of the oldest 
paving-brick in the country were made from this class of clays, notwith¬ 
standing that they exhibit a very high absorption of water. 

Shales. 

The shales, or those hard, consolidated, laminated, rock-like clays that 
are also popularly called “ soapstone” and “soft slate,” are now almost 
•exclusively used in the manufacture of paving-brick. They occur in very 


198 


THE MATERIALS OF CONSTRUCTION. 


much larger and thicker bodies than either the surface clays or fire-clays, 
often outcropping as low hills, and they can usually be cheaply worked by 
steam-shovels in open pits. While they are usually non-plastic as they 
occur in the bank, they can be easily ground to powder, when they readily 
work up into a plastic mass with water. The shales are usually very high 
in fluxing impurities, and this is the reason why they are so favorably 
adapted for paving-brick, as this enables them to be readily vitrified. The 
average composition of the shales that have proved eminently satisfactory 
for this purpose is as follows: 

Silica (Si0 2 )... 56 per cent. 

Alumina (A1 2 0 3 ). 22 “ 

Ignition loss (chemically combined water). 7 “ 

Moisture (H 2 0). 2 “ 


Total non-fluxing constituents 


Sesquioxide of iron (Fe„(X). 7 per cent. 

Lime (CaO). 1 “ 

Magnesia (MgO). 1 “ 

Alkalies (K 2 0Na 2 0). 4 “ 


Total fluxing constituents 


87 per cent. 


13 per cent. 


Grand total. 100 per cent. 

While the best shales range quite closely around the preceding analysis, 
quite a range in the fluxing constituents is permissible, as the chemical 
analysis is always very secondary in the consideration of clays. All clays, 
for any purpose whatever, depend primarily on their physical properties, 
and if these are not favorable the chemical composition is of no importance. 
A very elaborate discussion of the chemical composition and the influence 
of the impurities of clays is given by the writer in Part I. of the “Report 
on the Missouri Clays,” to which the readerps referred for details which it 
is impossible to discuss in this brief chapter.* 

172. Physical Properties of Clays. —The physical properties of clay, on 
which depend its manufacture and uses, consist of the following factors: 

I. Plasticity; 

II. Shrinkage in drying and burning; 

III. Speed in drying, burning, and cooling; 

IV. Point of incipient, complete, and viscous vitrification; 

V. Density before and after burning; 

VI. Colors of burned ware; 

VII. Strength of burned ware. 


Plasticity. 

Plasticity is the most important quality of any clay, as its ability to be 
moulded depends upon this property. When mixed with the proper 


* To be obtained from the State Geologist, Jefferson City, Mo. 





















THE MANUFACTURE OF VITRIFIED PAVING-BRICK. 


199 


amoufit of water it is called fat when it is very plastic, and the more 
plastic the clay the stronger the brick will be. In making paving-brick, 
excessive plasticity is found to increase the defect of laminations, which 
is a great source of weakness if excessively developed. To counteract this 
trouble the clay is either mixed with a less plastic one, or with sand, “grog,” 
or other lean materials which reduce the plasticity. 

Shrinkage. 

The shi mka 0 e is a vei y important factor in determining the size of 
moulds and dies to produce a given-sized brick after burning. The drying 
shrinkage is the reduction of volume which takes place when the soft mud 
brick becomes dry from the elimination of the water used in moulding, 
which amounts to 3 to 7 per cent. A second shrinkage occurs when the 
dried brick is burned, which is greater the harder the brick is burned, until 
thoroughly vitrified, when it ceases to shrink. The fire shrinkage varies 
from 4 to 8 per cent, and the total shrinkage ranges from 7 to 15 per cent. 

Speed of Drying, etc. 

The speed of drying, burning, and cooling are extremely important 
factors to the manufacturer in determining the size of his plant, besides 
being of great importance in affecting the strength of the brick. Some 
clays can be rapidly dried, burned, and cooled without having their strength 
seriously impaired, while others are very much weakened, if not actually 
cracked or ruptured, unless this is carried on very slowly. As a broad rule, 
the more plastic a clay the more slowly it must be dried, burned, and cooled, 
while the coarser and leaner clays can be treated much more rapidly with¬ 
out detriment. This is a factor that is keenly appreciated by the manu¬ 
facturer, but is rarely understood or appreciated by the engineer, yet it 
affects the strength of the brick more than any one factor. It does not 
follow that a clay that requires to be slowly dried must necessarily be 
slowly heated and cooled, or vice versa; for there is an individuality about 
clays that requires a separate determination of each of these factors as to 
their amount and influence. 

Vitrification. 

The stages of (1) incipient, (2) complete, and (3) viscous vitrification 
are extremely important, as paving-brick should be raised to at least the 
stage of incipient vitrification to secure the requisite density, hardness, low 
absorption, and toughness; while it must not be raised to the point of 
viscous vitrification, as it then loses its shape. In the shales suitable for 
paving-brick the first stage is reached at from 1500° to 1800° F., and the 
second at 1800° to 2200° F., or at a very bright cherry-red. 

Density. 

The denser the clay the denser the brick made therefrom will be, and 
the higher the density the more durable the brick. The specific gravity 


200 


TEE MATERIALS OF CONSTRUCTION. 


of shales usually range from 2.10 to 2. GO, and the specific gravity of the 
brick will be about the same. The impure fire-clay brick are generally some¬ 
what lighter, or vary from 1.95 to 2.30, but the brick have a specific 
gravity somewhat lower than that of the original fire-clay. 

Color. 

The color of paving-brick is of great local importance in estimating the 
degree to which it has been burned, and the care with which it has been 
handled. If the shale is high in iron (which is usually the case) the result¬ 
ant brick varies from red to very dark brown in color, while if the clay is. 
low in iron and high in lime it is light in color. Furthermore, the skill 
of the burner is able to largely influence the color by the manipulation of 
his fires, so that general rules for determining the quality of paving-brick 
by color only are dangerous, though for specific cases and a given burner 
they are of very great aid in quickly arriving at the quality of the brick. 

THE MANUFACTURE OF PAVING-BRICK. 

173. Preparing the Clays.—The surface clays are usually obtained by 
either the pick and shovel, plough and scraper or clay gatherer, or the 
steam-shovel and cars, according to the size of the yard and local conditions. 
The fire-clays, as they usually occur underground, are mined bv the room- 
and-pillar system, like coal, which is very much more expensive. The 
shales are sometimes worked by the room-and-pillar system, where they 
occur underground, but in most cases they are worked in open pits, by 
blasting, or else worked direct from the bank into the cars by powerful 
steam-shovels. 

The clays are sometimes pulverized by toothed rolls,'and occasionally by 
centrifugal disintegrators, but in most cases a revolving dry-pan with a 
perforated grate bottom is employed especially for shales and fire-clays. 

The crushed clay is usually screened in either revolving trommels, or 
fixed or shaking riddles, with 4 to 16 meshes to the linear inch. The 
degree of fineness of the screen is a very important matter, as the finer the 
clay the more plastic it is, and hence the stronger the brick. In some 
cases, however, excessive fineness causes checking and cracking in drying 
or burning, and aggravates the trouble from laminations, so that the fine¬ 
ness of the screen should be determined for each specific clay. Sometimes 
the clay is 'not screened any further than is accomplished by the screen- 
plates of the dry-pan, which are usually -J to £ inch in width. 

The screened clay is next mixed with water to a more or less plastic 
mass in a pug-mill. The pug-mill consists of a trough containing a revolv¬ 
ing shaft that is armed with blades set at an angle. It should revolve at 
such a speed, or the blades should be set at such low pitch, or the length 
should be sufficiently great, or the amount of clay to be pugged should be 
so restricted, as to secure a thorough , uniform mixture, of the clay and 
water; but frequently the pug-mills are too short to accomplish this, or they 






THE MANUFACTURE OF VITRIFIED PAVING-BRICK. 


201 


are overcrowded, or speeded too high, or the clay is run through too quickly 
by the blades being given an excessive pitch, and consequently the clay 
comes out with variable amounts of water. This causes checking and 
cracking in the drying, and sometimes in the burning, with marked varia¬ 
tions in the strength of the brick, besides causing the bar of clay to rag as 
it leaves the brick machine. The more thoroughly a clay is pugged, the 
more plastic it is rendered, and the more uniform and reliable will be the 
quality of the brick, and this department could be remodelled to decided 
advantage in most paving-brick plants. 

174. Moulding .—Three processes are employed for moulding paving 
brick, to wit: 

The Soft-mud Process; 

The Stiff-mud Process; 

The Semi-dry Process. 

In the Soft-mml Process the clay is mixed with sufficient water to 
make a very soft, extremely plastic mud, which is moulded by hand or 
soft-mud machines into imperfectly formed brick; these are allowed to 
partially dry, to a firm, stiff condition, and are then repressed into perfectly 
formed brick. This process makes an excellent quality of brick, but it 
necessitates a second handling of the brick during the drying stage. Out¬ 
side of a few small yards, it has been quite generally given up in the paving- 
brick trade, on account of the expense of the extra handling and breakage, 
besides considerable risk of injuring the strength of the brick, if they are 
allowed to get too dry. 

In the Stiff-mud Process the clay is pugged with sufficient water to 
make a stiff, plastic mud, which is forced through a die by a continuous- 
working auger or intermittent plunger, as a bar of clay, which is then cut 
by wires into suitable lengths. This is the process that is almost univer¬ 
sally employed in the manufacture of vitrified brick, as the mud is stiff 
enough to be made into perfectly shaped brick, which can be loaded on to 
cars without risk of being marked or injured in handling. 

In extruding the bar of clay from the brick machine, two types of dies 
are employed: in one the bar of clay is approximately 3" x 4" in section, 
which is cut into 9" lengths, and is known as the “ end-cut system while 
in the other the die is approximately 4" X 9" in section, and the bar is cut 
into 3" lengths, which is known as the “ side-cut system.” There is con¬ 
siderable difference of opinion as to the relative merits of these two methods 
of moulding, which too frequently is founded on very diversified facts. If 
the clay is lean or sandy, the side-cut brick is apt to be of better quality 
than the end-cut; while if the clay is very fine and eminently plastic, the 
end-cut system gives fewer laminations and a superior quality to the side- 
cut. 

Jn the Semi-dry Process the clay is mixed with just enough water to 
dampen it, so that it adheres slightly when firmly pressed. The brick are 


202 


THE MATERIALS OF CONSTRUCTION. 


moulded by feeding the damp clay into a mould-box, in which it is sub¬ 
jected to a very heavy pressure by a reciprocating plunger. This process 
has been used to a very limited extent for paving-brick, as the brick are 
not as tough as when made by the mud process, while it is much more 
difficult to burn a large percentage of No. 1 grade. As there is consid¬ 
erable difficulty in feeding the mould-boxes with damp clay, the moulds 
are frequently only imperfectly filled, which prevents the brick from 
receiving the heavy pressure necessary to bond it, besides causing imperfect 
faces. 

Repressing .—Recently there has been a heavy demand for repressing 
the brick made by the stiff-mud process immediately after it leaves the 
brick machine. In the repressing process the brick is exposed to a mod¬ 
erate vertical pressure in a metal mould-box, while still in a plastic condi¬ 
tion, which thoroughly fills out the edges and angles, and rounds them if 
desired. This results in a brick of uniform size and perfect shape, so that 
the appearance of the brick is greatly improved ; but as the pressure is 
moderate, it is doubtful if the quality of the brick is enhanced by this 
extra operation. Where there have been opportunities for testing the 
relative merits of the same clay in repressed and unrepressed brick, the 
facts indicate that the strength of the brick is endangered by breaking the 
structure formed in the slow-acting brick-machine by subjecting it to such 
radically different forces as occur in a vertical-acting, quickly applied 
repress. Thus some Purington unrepressecl brick have been exposed for 
two years on Lasalle Street, Chicago, to the heaviest kind of metropolitan 
traffic, which it has very successfully withstood; while repressed brick 
from the same plant has not stood so well on other Chicago streets with 
much less traffic. This is a matter that needs further investigation and 
more facts, and the above is the most important evidence known to the 
writer that bears directly on this question. * 

175. Drying and Burning.— Drying. — 1 The moulded brick are hacked 
on cars, in open checkerwork, direct from the brick-machine, which are run 
in drying-tunnels, where they are exposed for 24 to GO hours to light open 
fires, or to a heated blast, or to the radiation of an extensive series of steam- 
pipes, in order to expel the water used in moulding. Some clays can be 
safely dried in 18 to 30 hours without checking or cracking, while others 
have their strength seriously impaired unless the drying takes from 48 to 
72 hours. Usually the finer and more plastic the clay the greater the time 
required, while the coarser and leaner the clay the more rapidly it can be 
dried. 

Burning .—Three classes of kilns are employed in burning: the up¬ 
draught, the down-draught, and the continuous. The up-draught kiln, 
which is the type usually employed in burning building-brick, has a series 
of parallel fires at the bottom of the kiln, from which the heat rises through 
the brick, and escapes at the top of the kiln. The brick that are directly 
exposed to the fire at the bottom r^oeive too much heat, while the brick at 

* Recent (1896) rattler tests by Prof. Orton, on bricks made from the same clay, on 
different machines, and burned together in the same kiln, indicate clearly that repress¬ 
ing an end cut brick benefits it, while repressing a side-cut brick injures it. 





THE MANUFACTURE OF VITRIFIED PAVING-BRICK. 


203 


the toj) of the kiln do not receive sufficient heat to vitrify them. There 
is, consequently, a goodly percentage of overburned, misshapen brick at the 
bottom of the kiln, and a heavy percentage of soft, unburned brick at the 
top, the central portion being the only part that receives the proper degree 
of heat. As the percentage of No. 1 brick, or those suitable for paving, 
ranges from 35 to 65 per cent, according to the skill of the burner, the up¬ 
draught type of kiln is seldom employed for paving-brick. In the down¬ 
draught type of kiln the heat rises to the top or crown of the kiln from a 
series of outside fires, and then passes down through the brick to flues at 
the bottom of the kiln, and then escapes to one or more stacks. The brick 
are protected from excessive heat, and the heat is more thoroughly and 
completely distributed through the brick than in the up-draught type. The 
percentage of first-class brick is therefore much greater, as with intelligent 
handling from 60 to 90 per cent of No. 1 pavers can be obtained. 

The down-draught kilns were formerly of the round or beehive type, 
which hold from 25,000 to 75,000 brick; but in recent practice the long 
rectangular design is preferred, which hold from 100,000 to 300,000 brick, 
and most of the paving-brick are burned to-day in kilns of this design. 

In the continuous type of kiln the coal is fed directly in among the brick, 
which are piled in a long tunnel, and the heat is drawn through them by a 
high stack at the opposite end. This results in a great economy of fuel 
over both the up-draught and down-draught types of kiln; but the shrinkage 
and the difficulty of securing uniformity in burning is so great that they 
only yield from 40 to 70 per cent of No. 1 pavers, and they are not generally 
used. 

The practice of glazing paving-brick with salt, similar to sewer-pipe, was 
formerly employed to a considerable extent, as it gave the brick a dark color, 
which was supposed to indicate hardness, besides rendering defects less con¬ 
spicuous. As the glaze is superficial, it adds nothing to the durability of 
the brick, while it greatly increases the difficulty of sorting by color, and 
•enables soft brick to be overlooked unless very thoroughly inspected. The 
practice is to be strongly deprecated, and it is dying out. 

176. Annealing.—After the brick have been burned, the kiln should be 
tightly closed to shut off the access of cold air, and the longer the time given 
the brick to cool and anneal the tougher the brick will be. Bricks made 
from the best clays can be ruined by cooling off the kiln too rapidly. If 
this does not result in checking the brick it will at least make them brittle. 
The conductivity of clay for heat is so feeble that unless the brick are 
very slowly cooled internal stresses are produced—very much as in rapidly 
cooled steel or glass—which interfere with the toughness of the brick. 
This annealing or toughening by slow cooling is not appreciated by 
eimineers though well understood by the brickmakers. They claim they 
cannot afford to take the time in cooling off the kilns that they would like 
to. where the price is the criterion that will determine the successful bidder, 
while quality is made subordinate. The kilns are the most expensive portion 


204 


TEE MATERIALS OF CONSTRUCTION. 


in a paving-brick plant, and delay in emptying them by slow cooling adds, 
considerably to the expense of manufacture; so that unless the brick- 
makers are paid accordingly, they cannot afford to anneal with the care 
that is demanded for the best quality of brick. The usual practice in 
brickyards is to “ turn ” or fill a kiln once a month, which allows from six 
to nine days for cooling off. If the kiln capacity of a yard could be in¬ 
creased 25 per cent so as to give the kilns twice the time to cool off, it 
would result in a very much tougher, more uniform, and reliable brick; 
but it would necessitate a price commensurate with this increased outlay 
of capital, as there would be no increase in the quantity of brick produced. 

Where the very best quality of paving-brick is required, a matter of $1.00 
or $2.00 increase in the cost of the brick to insure thorough annealing would 
prove to be very great economy, and a very judicious investment, in greatly 
increasing the durability of the pavement. 

177. Sorting .—In emptying the kiln there are usually three grades of 
brick made in the vitrified trade. In the down-draught type of kiln, one or 
two top courses are liable to be air-checked and more or less brittle if the 
kiln is either improperly designed or improperly handled in burning, while 
the top layer is always covered with soot and ashes that mars and stains the 
surface of the brick. As these brick get the highest heat they are usually 
the hardest, and while not generally tough enough for paving purposes, they 
are very desirable brick for sewers, foundations, and sidewalks, especially as 
they are free from kiln-marks, and are seldom misshapen. The first two or 
three layers are therefore usually set aside and sold as sewer and sidewalk 
brick. 

The bottom portion of the kiln, or the lower two to ten courses, do not 
usually receive sufficient heat to be properly vitrified, and are known as No. 
2 or building brick, as they are well adapted for foundations or for backing- 
stock brick. 

The intermediate or central portion of the kiln are No. 1, or strictly 
first-class, paving-brick, which are distinguished by the fracture, toughness, 
hardness, and the color from the other two grades of brick. They should be 
perfectly uniform on the fracture, homogeneous, very dense, very hard, 
tough, and reasonably free from “ kiln-marks,” or indentations made by 
overhung brick. 

Kiln-maTks are a splendid guide that the brick have received sufficient 
heat to vitrify them, and the greater the depth of the kiln-mark the more 
thoroughly the brick is usually vitrified; but if too deep they make a rough, 
uneven pavement. There is usually a limit as to what is allowable for the 
depth of the kiln-mark, which is a matter of opinion for the engineer, and 
is placed at ^ to § inch. Except in fire-clays, it is seldom that a properly 
vitrified brick is entirely free from slight indentations, unless from the 
very top of the kiln; with the exception of this one place, a total absence of 
such marks is apt ro indicate underburning. 






CHAPTER XIII. 


TIMBER.* 

CHARACTERISTICS AND PROPERTIES OF WOOD. 

178. Structure and Appearance.—The structure of wood affords the only 
reliable means of distinguishing the different kinds. Color, weight, smell, 
and other appearances, which are often direct or indirect results of struc¬ 
ture, may be helpful in this distinction, but cannot be relied upon entirely. 
In addition, structure underlies nearly all the technical properties of this 
important product and furnishes an explanation why one piece differs as to 
these properties from another. 

Structure explains why oak is heavier, stronger, and tougher than pine; 
why it is harder to saw and plane, and why it is so much more difficult to. 
season without injury. From its less porous structure alone, it is evident 
that a piece of a young and thrifty oak is stronger than the porous wood of 
an old or stunted tree ; or that Georgia or long-leaf pine excels white pine- 
in weight and strength. Keeping especially in mind the arrangement and 
direction of the fibres of wood, it. is clear at once why knots and “ cross¬ 
grains ” interfere with the strength of timber. 

It is due to structural peculiarities that “ honeycombing ” occurs in 
rapid seasoning, that “checks” or cracks extend radially and follow pith- 
rays, that tangent or “ bastard ” boards shrink and warp more than quar¬ 
tered lumber. These same peculiarities enable cherry and oak to take a 
better finish than basswood or coarse-grained pine. 

Moreover, structure, aided by color, determines the beauty of wood. 
All the pleasing figures, whether in a hard-pine ceiling, a desk of Quar¬ 
tered oak, or in the beautiful panels of “curly” or “bird’s-eye” maple 
decorating the saloon of a ship or a palace-car, are due to differences in the 
structure of the wood. Knowing this, the appearance of any particular 


* This chapter is taken from Bulletin 10 of the U. S. Forestry Division, Agricultural 
Department, 1895 ; B E. Feruow, Chief of the Division. The matter contained in this 
bulletin is mostly the result of original studies made by Mr. Filibert Roth, this work 
being one department of the “ U. S. Timber Investigations. 


205 






206 


THE MATERIALS OF CONSTRUCTION. 


section can be foretold, and almost unlimited choice and combination are 
thereby suggested. 

Thus a knowledge of structure not only enables us to distinguish the 
different woods, judge as to their qualities, and explain the causes of their 
beauty, but it also becomes an invaluable aid to the thoughtful worker, 
guiding him to a more careful selection and a more perfect use of his 
material. 

179. Classes of Trees.—The timber of the United States is furnished 
by three well-defined classes of trees: the needle-leaved, naked-seeded coni¬ 
fers (pine, cedar, etc.); the dicotyledonous (with two seed-leaves), broad¬ 
leaved trees (oak, poplar, etc.) ; and to an inferior extent by the monocoty- 
ledonous (with one seed-leaf), palms, yuccas, and their allies, which last are 
confined to the most southern parts of the country. 

Broad-leaved trees are also known as deciduous trees, although, es¬ 
pecially in warm countries, many of them are evergreen,* while the coni¬ 
fers are commonly termed “ evergreens/’ although the larch, bald cypress, 
and others shed their leaves every fall, and even the names “ broad-leaved ” 
and “ coniferous/’ though perhaps the most satisfactory, are not at all 
exact, for the conifer ginkgo has broad leaves and bears no cones. 

In the lumber trade, the woods of broad-leaved trees are known as 
“ hardwoods,” though poplar is as soft as pine, and the coniferous woods 
are “ soft woods,” notwithstanding that yew ranks high in hardness even 
when compared to “ hardwoods.” 

Both in the number of different kinds of trees or species and still 
more in the importance of their product the conifers and broad-leaved trees 
far excel the palms and their relatives. 

In the manner of growth both conifers and broad-leaved trees behave 
alike, adding each year a new layer of wood which covers the old wood in 
all parts of the stem and limbs. Thus the trunk continues to grow in 
thickness throughout the life of the tree by additions (annual rings) which 
in temperate climates are, barring accidents, accurate records of the tree. 
With the palms and their relatives the stem remains generally of the same 
diameter, the tree of a hundred years being no thicker than it was at ten 
years, the growth of these being only at the top. Even where a peripheral 
increase takes place, as in the yuccas, the wood is not laid on in well- 
defined layers; the structure remains irregular throughout. 

Though alike in their manner of growth, and therefore similar in their 
general make-up, conifers and broad-leaved trees differ markedly in the de¬ 
tails of their structure and the character of their wood. The wood of all 
conifers is very simple in its structure, the fibres composing the main part 
of the wood being all alike and their arrangement regular. The wood of 
broad-leaved trees is complex in structure; it is made up of several differ- 


* In Ceylon even the cultivated cherry has become an evergreen. 





TIMBER. 


20? 


ent kinds of cells and fibres and lacks the regularity of arrangement so 
noticeable in the conifers. This difference is so great that in a study of 
wood structure it is best to consider the two kinds separately. 

180. Sapwood and Heartwood.—Examining a smooth cross-section or 
end face of a well-grown log of Georgia pine or Norway pine, we distin¬ 
guish an envelope of reddish, scaly bark, a small whitish pith at the centre, 
and between these the wood in a great number of concentric rings. 

A zone of wood next to the bark, 1 to 3 or more inches wide, and con¬ 
taining thirty to fifty or more annual rings, is of lighter color; this is the 
sapwood, the inner, darker part of the log being the heartwood. In the 
former many cells are active and store up starch and otherwise assist in 
the life-processes of the tree, although only the last or outer layer of cells 
(the cambium layer) forms the growing part and the true life of the tree. 
In the heartwood all cells are lifeless cases, and serve only the mechanical 
function of keeping the tree from breaking under its own great weight, or 
from being broken by the winds. 

The darker color of the heartwood is due to infiltration of chemical sub¬ 
stances into the cell-walls, but the cavities of the cells in pine are not filled 
up, as is sometimes believed, nor do their walls grow thicker, nor is their 
wall any more lignified than in the sapwood. Sapwood varies in width and 
in the number of rings which it contains, even in different parts of the 
same tree; the same year’s growth which is sapwood in one part of a disk 
may be heartwood in another. Sapwood is widest in the main part of 
the stem and varies often within considerable limits, and without apparent 
regularity. Generally it becomes narrower toward the top and in the 
limbs, its width varying with the diameter, and being least, in a given disk, 
on the side which has the shortest radius. Sapwood of old and stunted 
pines is composed of more rings than that of young and thrifty specimens. 
Thus in a pine two hundred and fifty years old, a layer of wood or annual 
ring does not change from sapwood to heartwood until seventy or eighty 
years after it is formed, while in a tree one hundred years old, or less, it 
remains sapwood only from thirty to sixty years. The width of the sap- 
wood varies considerably for different kinds of pines; it is small for long- 
leaf and white pine, and great for loblolly and Norway pines. Occupying 
the peripheral part of the trunk, the proportion which it forms of the 
entire mass of the stem is always great. Thus even in old trees of long-leaf 
pine the sapwood forms about 40 per cent of the merchantable log, while 
in the loblolly and in all young trees the bulk of the wood is sapwood. 

181. The Annual Rings.—The concentric, annual, or yearly, rings 
which appear on the end face of a log are cross-sections of so many thin 
layers of wood. Each such layer forms an envelope around its inner 
neighbor, and is in turn covered by the adjoining layer without, so that 
the whole stem is built up of a series of thin hollow cylinders, or rather 
cones. A new layer of wood is formed each season, covering the entire 


208 


THE MATERIALS OF CONSTRUCTION 


stem, as well as all the living branches. The thickness of this layer, or 
the width of the yearly ring, varies greatly in different trees and also in 
different parts of the same tree. In a normally grown, thrifty pine log 
the rings are widest near the pith, growing more and more narrow 
toward the bark. Thus the central twenty rings in a disk of an old 
long-leaf pine may each be one-eighth to one-sixth inch (3 to 4 mm.) wide, 
while the twenty rings next to the bark may average only one-thirtieth 
inch (0.8 mm.). In our forest trees rings of one-half inch in width occur 
only near the centre in disks of very thrifty trees of both conifers and hard 
woods; one-twelfth inch represents good thrifty growth, and the minimum 
width of about one two-hundredths inch (0.12 mm.) is often seen in stunted 
spruce and pine. The average width of rings in well-grown old white pine 
will vary from one-twelfth to one-eighteenth inch, while in the slower grow¬ 
ing long-leaf pine it may be one twenty-fifth to one fiftieth of an inch. 
The same layer of wood is widest near the stump in very thrifty young 
trees, especially if grown in the open part, but in old forest trees the same 

• 

year’s growth is wider in the upper part of the tree, being narrowest near 
the stump and often also near the very tip of the stem. Generally the 
rings are widest near the centre, growing narrower towards the bark. In 
logs from stunted trees the order is often reversed, the interior rings being 
thin and the outer rings widest. Frequently, too, zones or bands of. very 
narrow rings, representing unfavorable periods of growth, disturb the 
general regularity. Few trees, even among pines, furnish logs with truly 
circular cross-sections; usually they are oval, and at the stump commonly 
quite irregular in figure. Moreover, even in very regular or circular disks 
the pith is rarely in the centre, and frequently one radius is conspicuously 
longer than its opposite, the width of some of the rings, if not all, being 
greater on one side than on the other. This is nearly always so in the 
limbs, the lower radius exceeding the upper. 

In extreme cases, especially in the limbs, a ring is frequently conspicuous 
on one side and almost or entirely lost to view on the other. Where the 
rings are extremely narrow, the dark portion of the ring is often wanting, 
the color being quite uniform and light. The greater regularity or irregu¬ 
larity of the annual rings has much to do with the technical qualities of 
the timber. 

182. Spring and Summer Wood (Coniferous Trees).—Examining the 
rings more closely, it is noticed tha„ each ring is made up of an inner, 
softer, light-colored, and an niter, or peripheral, firmer and darker-colored 
portion. Being formed in the fore part of the season, the inner, light- 
colored part is termed spring wood, the outer, darker portion being the 
summer wood of the ring. Since the latter is very heavy and firm, it de¬ 
termines to a large extent the weight and strength of the wood, and as its 
darker color influences the shade of color of the entire piece of wood, this 
color effect becomes a valuable aid in distinguishing heavy and strong 





TIMBER. 


209 


from light and soft pine wood. In most hard pines, like the long-leaf, 
the dark summer wood appears as a distinct band, so that the yearly 
ring is composed of two sharply defined bands—an inner, the spring wood, 
and an outer, the summer wood. But in some cases, even in hard pines, 
and normally in the wood of white pines, the spring wood passes gradually 
into the darker summer wood, so that a sharply defined line occurs only 
where the spring wood of one ring abuts against the summer wood of 
the previous year’s growth. It is this clearly defined line which en¬ 
ables the eye to distinguish even the very narrow rings in old pines 
and spruces. In some cases, especially in the trunks of Southern pines, 
and normally on the lower side of pine limbs, there occur dark bands of 
wood in the spring-wood portion of the ring, giving rise to false rings 
which mislead in a superficial counting of rings. In the disks cut from 
limbs these dark bands often occupy the greater part of the ring and appear 
as “limes” or sickle-shaped figures. The wood of these dark bands is 
similar to that of the true summer wood—the cells have thick walls, but 
usually lack the compressed or flattened form. 

Normally, the summer wood forms a greater proportion of the ring in 
the part of the tree formed during the period of thriftiest growth. In an 
old tree this proportion is very small in the first two to five rings about the 
pith, and also in the part next to the bark, the intermediate part showing 
a greater proportion of summer wood. It is also greatest in a disk taken 
from near the stump and decreases upward in the stem, thus fully account¬ 
ing for the difference in weight and firmness of the wood of these different 
parts. In the long-leaf pine the more substantial summer wood often forms 
scarcely 10 per cent of the wood in the central five rings; 40 to 50 per cent 
of the next one hundred rings; about 30 per cent in the next fifty, and 
only about 20 per cent in the fifty rings next to the bark. It averages 45 
per cent of the wood of the stump and ouly 24 per cent of that of the top. 

Sawing the log into boards, the yearly rings are represented on the faces 
of the middle board (radial sections) by narrow, parallel stripes (see Fig. 84), 
an inner, lighter stripe, and its outer, darker neighbor, always corres¬ 
ponding to one annual ring. 

On the faces of the boards nearest the slab (tangential or “bastard” 
boards) the several years’ growth should also appear as parallel but much 
broader stripes. This they do only if the log is short and very perfect. 
Usually a variety of pleasing patterns is displayed on the boards, depend¬ 
ing on the position of the saw-cut and on the regularity of growth of 
the log. (See Fig. 84.) 

Where the cut passes through a prominence (bump or crook) of the log, 
irregular, concentric circlets and ovals are produced, and on almost all 

tangent boards V-shaped forms occur. 

183. Anatomical Structure of Coniferous Woods.— Holding a well- 
smoothed disk or cross-section one-eighth inch thick toward the light, it is 


210 


THE MATERIALS GF CONSTRUCTION. 


readily seen that pine wood is a very porous structure. If viewed with a 
strong magnifier, the little tubes, especially in the spring-wood of the rings, 
are easily distinguished and their arrangement in regular straight radial 
rows is apparent. Scattered through the summer-wood portion of the rings, 
numerous irregular grayish dots (the resin-ducts) disturb the uniformity 
and regularity of the structure. Magnified one hundred times, a piece of 
spruce, which is similar to pine, presents a picture like that shown in Fig. 
85. Only short pieces of the tubes or cells of which the wood is com¬ 
posed are represented in the picture. 



Fig. 84.—Board of Pine. CS, cross-section ; 
RS , radial section ; TS, tangential section ; 
sic , summer wood ; spic, spring wood.* 



Fig. 85.—Wood of Spruce. 1, natural size; 
2, small part of one ring magnified 100 
times. The vertical tubes are wood fibres, 
in this case all “ tracheids.” m, medullary 
or pith ray; n, transverse tracheids or pith- 
ray; a, b, and c, bordered pits of the tra¬ 
cheids, more enlarged. 


The total length of these fibres is one-twentieth to one-fifth inch, being 
smallest near the pith, and is fifty to one hundred times as great as their 
width (Fig. SC). They are tapered and closed at their ends, polygonal or 
rounded'and thin-walled, with a large cavity (lumen) or internal space in 
the spring wood, while they are thick-walled and flattened radially, with the 
internal space or lumen much reduced, in the summer wood. (See right-hand 
portion of Fig. 85.) This flattening, together with the thicker walls of the 
cells which reduces the lumen, produces the greater firmness and darker 


* This figure is deceptive inasmuch as the more open or porous spring wood is repre¬ 
sented by a plain white surface, as though it were solid, while the more solid summer 
wood is represented by a shaded surface as though it were more porous. The reverse is 
of course the case.—J. B. J. 




















































































































































Fig, 86.—Group of Fibres from Pine Wood. Partly schematic. The little circles are “ bordered-pits ” (see Fig. 85, a-c). The transverse row 
of square pits indicate the places of contact of these fibres and the cells of the neighboring pith-rays. Magnified about 50 times 


TIMBER . 


211 



color of the summer wood; that is to sav, there is more 
material in the same volume. As shown in the figure, 
the tubes, cells, or “ tracheitis” are decorated on their 
walls by circlet-like structures, called “ bordered pits,” 
sections of which are seen more magnified at a , b, and 
c, Fig. 85. These pits are in the nature of pores, cov¬ 
ered by very thin membranes, and serve as waterways 
between the cells or tracheids. 

The dark lines on the side of the smaller piece (1* 
Fig. 85) appear when magnified (in 2, Fig. 85) as tiers 
of eight to ten rows of cells, lying in vertical radial 
planes, and are seen as bands on the radial face, and as 
rows of pores on the tagential face. These bands or 
tiers of cell-rows are the “ medullary rays ” or “pith- 
ravs,” and are common to all our lumber woods. In 
the pines and other conifers they are quite small, but 
they can readily be seen, even without a magnifier, if a 
radial surface of split wood (not smooth) is examined. 
The entire radial face will be seen almost covered 
with these tiny structures, which appear as hue but 
conspicuous cross-lines. As shown in Fig. 85, the cells 
of the medullary or pith rays are smaller and very 
much shorter than the wood-fibres or tracheids, see 
b, Fig. 90, and their long axis is at right angles to that 
of the fibres. In pines and spruces the cells of the 
upper and lower rows of each tier or pith-ray have 
“ bordered ” pits like those of the wood-fibres or tra¬ 
cheids proper, but the cells of the intermediate rows, 
and of all rows in the rays of cedars, etc., have only 
“simple” pits, i.e., pits devoid of the saucer-like 
“ border” or rim. 

In pine, many of the pith-rays are larger than the 



Fig. 87 .— Block of Oak. C.S., cross section ; B.S., radial 
section; T.S., tangential section; m.r ., medullary or pith ray; 
a, height, b, width, and e, length of a pitli-ray. 









































































































































212 


THE MATERIALS OF CONSTRUCTION. 


majority, each containing a whitish line, the horizontal resimduct, which, 
though much smaller, resembles the vertical ducts seen on the cross-section. 
The larger vertical resin-ducts * are best observed on the removal of the bark 
from a fresh piece of white pine, cut in winter, where they appear as con¬ 
spicuous white lines, extending often for many inches up and down the stem. 

Neither the horizontal nor the vertical resin-ducts are vessels or cells, 
but are openings between cells, i.e., intercellular spaces in which the resin 
accumulates, freely oozing out when the ducts of a fresh piece of sap- 
wood are cut. They are present only in our coniferous woods, and even 
here they are restricted to pine, spruce, and larch, and are normally absent 
in fir, cedar, cypress, and yew. 

Altogether the structure of coniferous wood is very simple and regular, 
the bulk being made up of small fibres called tracheids, the disturbing ele¬ 
ments of pith-rays and resin-ducts being insignificant, and hence the great 
uniformity and great technical value of coniferous wood. 

184. Anatomical Structure of Broad-leaved Trees.—On a cross-section 

of oak, the same arrangement of 
pith and bark, of sapwood and 
heartwood, and the same disposi¬ 
tion of the wood in well-defined 
concentric or annual rings occurs, 
but the rings are marked by lines, 
or rows, of conspicuous pores or 
openings which occupy the 
greater part of the spring wood 
of each ring (see Fig. 87, also 
Fig. 89) and are, in fact, the 
openings through the vessels cut 
by the section. 'On the radial 
section, or quarter-sawed board, 
the several layers appear as so 
many parallel stripes (see Fig. 
88); on the tangential section or 
“ bastard ” face, patterns similar 
to those mentioned for pine wood 
are observed. But while the pat¬ 
terns in hard pine are marked by 
the darker summer wood and are 
Fig. 88.—Board of Oak. CS, cross-section ; RS, composed of plain, alternating 
radial section; T8, tangential section;®, vessels stripes of darker and lnditer 
01 - pores, cut through; A, slight curve in log wood> the flgnre8 iu Oakland 

which appears in section as an islet. ,, , . 

other broad-leaved woods) are 

due chiefly to the vessels, those of the spring wood in oak being the most 

* See rd, Fig. 118. 





















































TIMBER. 


213 


conspicuous (see Fig. 88); so that in an oak table the darker, shaded parts 
are the spring wood, the lighter parts the summer wood. 

On closer examination of the smoothed cross-section of oak, the spring- 
wood part of the ring is found to be formed, in great part, of pores: large, 
round, or oval openings through long vessels. These are separated by a 



grayish and quite porous tissue (see Fig. 89) which continues here and there 
in the form of radial, often branched, patches (not the pith-rays) into and 
through the summer wood to the spring wood of the next ring. The large 
vessels of the spring wood, occupying 6 to 10 per cent of the volume of a 
log in very good oak, and 25 per cent or more in inferior and narrow-ringed 
lumber, are a very important feature, since 
it is evident that the greater their share in 
the volume, the lighter and weaker the 
wood. They are smallest near the pith, and 
grow wider outward; they are wider in the 
stem than limb and seem to be of indefinite 
length, forming open channels in some cases 
probably as long as the tree itself. 

Scattered through the radiating gray 
patches of porous wood are vessels similar to 
those of the spring wood, but decidedly 
smaller. These vessels are usually fewer and 
larger near the spring wood, and smaller and 
more numerous in the outer portions of the Fig. 90.— Portion of the Firm Bodies 
rino- Their number and sizecan be utilized ofFibreswlthTwoCellsofaismall 

to distinguish the oaks classed as white oaks Pith - ra - v ' mr ' }UgMy masnified - 
from those classed as black and red oaks; they are fewer and larger in red 
oaks, smaller but much more numerous in white oaks. The summer wood, 
except for these radial grayish patches, is dark-colored and firm. This firm 
portion, divided into bodies or strands by these patches of porous wood and 
also by fine wavy concentric lines of short, thin-walled cells (see Fig. 89), 
consists of thick-walled fibres (see Fig. 90) and is the chief element of 





































































































214 


THE MATERIALS OF CONSTRUCTION. 




strength in oak wood. In good white oak it forms one half and more of the 
wood; it cuts like horn, and the cut surface is shiny and of a deep chocolate- 
brown color. In very narrow-ringed wood and in inferior red oak it 
is usually much reduced in quantity as well as quality. 

The pith-rays of the oak, unlike those of coniferous woods, are at 
least in part very large and conspicuous (see Fig. 87, their height in¬ 
dicated by the letter a, and their width by the letter I). The large 
medullary rays of oak are often twenty and more cells thick and sev¬ 
eral hundred cell-rows in height, which amount commonly to one or 
more inches. These large rays are con¬ 
spicuous on all sections. They appear as 
long, sharp, grayish lines on the cross-sec¬ 
tion, as short, thick lines, tapering at each 
end, on the tangential or “bastard” face, 
and as broad, shiny bands, the “silver 
grain” or “mirrors,” on the radial section. 

In addition to these coarse rays, there is 
also a large number of small pith-rays, 
which can be seen only when magnified. 

On the whole, the pith-rays form a much 
larger part of the wood than might be sup¬ 
posed. In specimens of good white oak it 
has been found that they formed about 1G 
to 25 per cent of the wood. 

185. Minute Structure. — If a well- 
smoothed, thin disk or cross-section of 
oak (say one-sixteenth inch thick) is held 
up to the light, it looks very much like a 
sieve, the pores or vessels appearing as 
clean-cut holes; the spring wood and gray 
patches are seen to be quite porous, but 
the firm bodies of fibres between them are 
dense and opaque. Examined with the 
magnifier it will be noticed that there is 
no such regularity of arrangement in 
straight rows as is conspicuous in the pine; 
on the contrary, great irregularity prevails. 

At the same time, while the pores are as 
as large as pin-holes, the cells of the denser 
Avood, unlike those of pine Avood, are too 
small to be distinguished. Studied with 
the microscope, each vessel is found to be a vertical roAv of a great 
number of short, wide tubes, joined end to end (Fig. 91,6*). The porous 
spring wood and radial gray tracts are partly composed of smaller vessels. 



Fig. 91.—Isolated Fibres and Cells. 

a, four cells of wood-parenchyma; 

b, two cells from a pith-ray; c, a 
single joint or cell of a vessel, the 
openings x leading into its upper 
and lower neighbors; d, traclieid; 
e, Avood-fibre proper. 

















































TIMBER. 


215 


but chiefly of tracheids like those of pine, and of shorter cells, the a wood- 
parenchyma, v ’ resembling the cells of the medullary rays. These latter, as 
well as the fine concentric lines mentioned as occurring in the summer wood, 
are composed entirely of short, tube-like parenchyma-cells with square or 
oblique ends (Fig. 91, a and b). The wood-fibres proper, which form the 
dark, firm bodies referred to, are very fine, thread-like cells one twenty-fifth 
to one-tenth inch long, with a wail commonly so thick that scarcely any 
empty internal space or lumen remains (Figs. 91, e, and 90). 

If instead of oak a piece of poplar or basswood (Fig. 92) had been used 
in this study, the structure would have been found to be quite different. 



92 —Cross-section of Basswood (magnified), v, vessels ; mr, pitli-rays. 

The same kinds of cell-elements, vessels, etc., are present, but their com¬ 
bination and arrangement is different, and thus from the great variety of 
possible combinations results the great variety of structure and, in conse¬ 
quence, of the qualities which distinguish the wood of broad-leaved trees. 
The sharp distinction of sapwood and heartwood is wanting; the rings are 
not so clearly defined, the vessels of the wood are small, very numerous, 
and rather evenly scattered through the wood of the annual ring, so that 
the distinction of the ring almost vanishes and the medullary or pith rays, 
in poplar, can be seen, without being magnified, only on the radial section. 

186. Different “Grains” of Wood—The terms “fine-grained,” “coarse¬ 
grained,” “straight-grained,” and “ cross-grained ” are frequently applied 
in woodworking. In common usage, wood is “ coarse-grained ” if its 
annual rings are wide, “ fine-grained ” if they are narrow; in the finer wood 
industries a “ fine-grained ” wood is capable of high polish, while a “ coarse¬ 
grained ” wood is not, so that in this latter case the distinction depends 
chiefly on hardness, and in the former on an accidental case of slo^\ oi 

rapid growth. 

Generally the direction of the wood-fibres is parallel to the axis of the 
stem or limb in which they occur, the wood is straight-grained, but in 
many cases the course of the fibres is spiral or twisted around the tree as 




216 


THE MATERIALS OF CONSTRUCTION 


shown in Fig. 93, and sometimes (commonly in butts of gum and cypress) 
the fibres of several layers are oblique in one direction, and those of the 


Fig. 93. Fig. 94. 

Fig. 93.—Spiral Grain. Season-checks, after removal of bark, indicate the direction of 
the fibres or grain. 

Fig. 94.— Alternating Spiral Grain in Cypress. Side and end view of same piece. When 
the bark was at o the grain at this point was straight. From that time each year it 
grew more oblique in one direction, reaching a climax at a , and then turned back in 
the opposite direction. These alternations were repeated periodically, the bark 
sharing in these changes. 





next series of layers are oblique in the opposite direction, as shown in 
Fig. 94; the wood is cross- or twisted-grained. Wavy grain in a tan¬ 
gential plane as seen on the radial section is illustrated in Fig. 94 a, which 

represents an extreme case observed in beech. 
This same form also occurs on the radial plane, 
causing the tangential section to appear wavy or 
in transverse folds. When wavy grain is fine, 
i.e., the folds or ridges small but numerous, it 
‘ gives rise to the “curly” structure frequently 
seen in maple. Ordinarily, neither wavy, spiral, 
nor alternate grain is visible on the cross-section; 
its existence often escapes the eye even on smooth, 
longitudinal faces in sawed material, so that the 
only safe guide to their discovery lies in splitting 
the wood in the two normal planes. 

Generally the surface of the wood under the bark, and therefore also 
that of any layer in the interior, is not uniform and smooth, but is chan¬ 
nelled and pitted by numerous depressions which differ greatly in size and 
form. Usually, any one depression or elevation is restricted to one or a 
few annual layers (i.e., seen only in one or a few rings), and is then lost,. 



Fig. 94 a .—Wavy Grain in 
Beech. (After Nordlinger.) 













































































TIMBER. 


217 


being compensated (the surface at the particular spot evened up) by growth. 
In some woods, however, any depression or elevation once attained grows 
from year to year and reaches a maximum size which is maintained for 
many years, sometimes throughout life. 

In maple, where this tendency to preserve any particular contour is 
very great, the depressions and elevations are usually small (commonly less 
than one-eighth inch, but very numerous. On 
tangent boards of such wood the sections of these 
pits and prominences appear as circlets and give 
rise to the beautiful “ bird’s-eye ” or “ land¬ 
scape ” structure. Similar structures in the burls 
of black ash, maple, etc., are frequently due to 
the presence of dormant buds, which cause the 
surface of all the layers through which they pass 
to be covered by small conical elevations, whose 
cross-sections on the sawed board appear as ir¬ 
regular circlets or islets each with a dark speck, 
the section of the pith or “ trace 99 of the dor¬ 
mant bud in the centre. 

In the wood of many broad-leaved trees the 
wood-fibres are much longer when full grown 
than when they are first formed in the cambium 
or growing zone. This causes the tips of each 
fibre to crowd in between the fibres above and 
below, and leads to an irregular interlacement of 
these fibres, which adds to the toughness but 
reduces the cleavability of the wood. 

At the junction of limb and stem the fibres 
on the upper and lower sides of the limb behave 
differently. On the lower side they run from the 
stem into the limb, forming an uninterrupted 
strand or tissue and a perfect union. On the 
upper side the fibres bend aside, are not con¬ 
tinuous into the limb, and hence the connection 
is imperfect (Fig. 95). 

Owing to this arrangement of the fibres, the 
cleft made in splitting never runs into the knot, 
if started on the side above the limb, but is apt 
to enter the knot if started below, a fact well 
understood in woodcraft. When limbs die, de¬ 
cay, and break off, the remaining stubs are sur¬ 
rounded and may finally be covered by the growth 
of the trunk, and thus give rise to the annoying 

187. Color and Odor.—Color, like structure, iends beauty to the wood. 



Fig. 95. —Section of Wood 
showing Position of the 
Grain at Base of a Limb 
which has been Dead Three 
Years. P, pith of both 
stem and limb ; 1-7, seven 
yearly layers of wood; a,, 
b, knot or basal part of a 
limb which lived f o u r 
vears, then died and broke 
off near the stem, leaving 
the part to the left of a, b, 
a “ sound ” knot, the part 
to the right a “ dead ” 
knot, which would soon be 
entirely covered by the 
growing stem. 

“ dead ” or “ loose ” knots. 
































































218 


THE MATERIALS OF CONSTRUCTION. 


aids in its identification, and is of great value in Vue determination of its 
quality. Considering only the heartwood, the black color of the per¬ 
simmon, the dark brown of the walnut, the light brown of the white oaks, 
the reddish brown of the red oaks, the yellowish white of the tulip and 
poplar, the brownish red of the redwood and cedar, the yellow of the papaw 
and sumac, are all reliable marks of distinction; and color together with 
lustre and weight are only too often the only features depended upon in 
practice. Newly formed wood, like that of the outer few rings, has but 
little color. The sapwood generally is light, and the wood of trees which 
form no heartwood changes but little, except when stained by forerunners 
of disease. 

The different tints of colors, whether the brown of oak, the orange- 
brown of pine, the blackish tint of walnut, or the reddish cast of cedar, are 
due to pigments, while the deeper shade of the summer-wood bands in pine 
and cedar, or in oak or walnut, is due to the fact that, the wood being 
denser, more of the colored wood substance occurs on a given space, i.e., 
there is more colored matter per square inch. 

Wood is translucent, a thin disk of pine permitting light to pass 
through quite freely. This translucency affects the lustre and brightness 
of lumber. When wood is attacked by fungi it becomes more opaque, loses 
its brightness, and in practice is designated “dead” in distinction from 
“live” or bright timber. Exposure to air darkens all wood; direct sun¬ 
light and occasional moistening hasten this change and cause it to pene¬ 
trate deeper. Prolonged immersion has the same effect, pine wood becom¬ 
ing a dark gray, while oak changes to a blackish brown. 

• Odor, like color, depends on chemical compounds, forming no part of 
the wood substance itself. Exposure to weather reduces and often 
changes the odor, but a piece of dry long-leaf pine, cedar, or camphor wood 
exhales apparently as much odor as ever when a new surface is exposed. 

Heartwood is more odoriferous than sapwood. Many kinds of wood are 
distinguished by strong and peculiar odors. This is especially the case 
with camphor, cedar, pine, oak, and mahogany, and the list would com¬ 
prise every kind of wood in use were our sense of smell developed in keep¬ 
ing with its importance. Decomposition is usually accompanied by pro¬ 
nounced odors; decaying poplar emits a disagreeable odor, while red oak 
often becomes fragrant, its smell resembling that of heliotrope. 

188. Resonance.—If a log or scantling is struck with the axe or hammer, 
a sound is emitted which varies in pitch and character with the shape and 
size of the stick, and also with the kind and condition of wood. Not only 
can sound be produced by a direct blow, but a thin board may be set vibrat¬ 
ing and be made to give a tone by merely producing a suitable tone in its 
vicinity. The vibrations of the air, caused by the motion of the strings of 
the piano, communicate themselves to the board, which vibrates in the 
same intervals as the string and reenforces the note. The note which a 


TIMBER. 


219 


given piece of wood may emit varies in pitch directly with the elasticity, 
and indirectly with the weight, of the wood. The ability of a properly 
shaped sounding-board to respond freely to all the notes within the range 
of an instrument, as well as to reflect the character of the notes thus 
emitted (i.e., whether melodious or not), depends, first, on the structure of 
the wood and next on the uniformity of the same throughout the board. 
In the manufacture of musical instruments all wood containing defects, 
knots, cross grain, resinous tracts, alternations of wide and narrow rings. 


and all wood in which summer and spring wood are strongly contrasted in 
structure and variable in their proportions, is rejected, and only radial 
sections (quarter-sawed or split) of wood of uniform structure and growth 
are used. 

The irregularity in structure, due to the presence of relatively large 
pores and pith-rays, excludes almost all our broad-leaved woods from such 
use, while the number of eligible woods among conifers is limited by the ne¬ 
cessity of combining sufficient strength with uniformity in structure, absence 
of too pronounced bands of summer wood, and relative freedom from resin. 

Spruce is the favored resonance wood; it is used for sounding-boards 
both in pianos and violins, while for the resistant back and sides of the latter 
the highly elastic hard maple is used. Preferably resonance wood is not 
bent to assume the final form; the belly of the yiolin is shaped from a 
thicker piece, so that every fibre is as nearly in its original unstrained con¬ 
dition as possible, and therefore free to vibrate. All wood for musical 
instruments is, of course, well seasoned, the final drying in kiln or warm 
room being preceded by careful seasoning at ordinary temperatures often 
for as many as seven years or more. The improvement of violins, not by 
age but by long usage, is probably due not only to the adjustment of the 
numerous component parts to each other, but also to a change in the wood 
itself; years of vibrating enabling any given part to vibrate much more 
readily. 

SPECIFIC GRAVITY, OR WEIGHT. 

189. Weight Dependent on Structure and Moisture.—A small cross- 
section of wood, as in Fig. 9G, dropped into water, sinks, showing that the 
substance of which wood-fibre or wood is built up is heavier 
than water. By immersing the wood successively in heavier 
liquids, until we find a liquid in which it does not sink, 
and comparing the weight of the same with water, we find 
that wood-substance is about 1.6 times as heavy as water, 
and that this is as true of poplar as of oak or pine. 

Separating a single cell, as shown in Fig. 97, a , drying 
and then dropping it into water, it floats. The air-filled 
cell-cavity or interior reduces its weight, and, like a corked 
empty bottle, it weighs less than the water. Soon, however, water soaks 
into the cell, when it fills up and sinks. 



Fig. 90. 
Cross - section 
of a Group of 
Wood fibres. 


220 


THE MATERIALS OF CONSTRUCTION. 


Many such cells grown together, as in a block of wood, sink when all or 
most of them are filled with water, but will float as long as the majority are 
empty or only partly filled. This is why a green, sappy pine pole soon 
sinks in “ driving ” (floating). Its cells are largely filled before it is thrown 
in, and but little additional water suffices to make its weight greater than 
that of the water. 

In a white-pine log, composed chiefly of empty cells (heartwood), the 
water requires a very long time to fill up the cells (five years would not 
suffice to fill them all), and therefore the log may float for many months or 
even years. When the wall of the wood-fibre is very thick (five-eighths or 
more of the volume), as in Fig. 97, b, the fibre sinks whether empty or filled. 

This applies to most of the fibres of the dark summer-w T ood 
bands in pines, and to the compact fibres of oak or hickory,, 
and many, especially tropical woods, have such thick-walled 
cells and so little empty or air space that they never float. 

Here, then, are the two main factors of weight in wood r 
The amount of cell-wall, or wood-substance, constant for any 
given piece, and the amount of water contained in the wood, 
variable even in the standing tree, and only in part eliminated 
in drying. 

The weight of the green wood of any species varies chiefly 
as the second factor, and is entirely misleading if the relative 
weight of different kinds is sought. Thus some green sticks 
of the otherwise lighter cypress and gum sink more readily 
than fresh oak. 

The weight of sapwood, or the sappy peripheral part of 
our common lumber woods, is always great whether cut in 
winter or summer. It rarely falls much below 45 pounds and 
commonly exceeds 55 pounds to the cubic foot, even in our lighter wooded 
species. 

It follows that the green wood of a sapling is heavier than that of an 
old tree, the fresh wood from a disk of the upper part of a tree often 
heavier than that of the lower part, and the wood near the bark heavier 
than that nearer the pith, and also that the advantage of drying the wood 
before shipping is most important in sappy and light kinds. 

When kiln-dried, the misleading moisture factor of weight is uniformly 
reduced and a fair comparison made possible. For the sake of convenience 
in comparison, the weight of wood is expressed either as the weight per cubic 
foot or, what is still more convenient, as specific weight or density. 

190. Variation in Weight in a Single Trunk.—If an old long-leaf pine 
is cut up as shown in Fig. 98, the wood of disk No. 1 is heavier than that 
of disk No. 2, the latter heavier than that of disk No. 3, and the wood of 
the top disk is found to be only about three fourths as heavy as that of 
disk No. 1. 


3 

Fig. 97. —Iso¬ 
lated Fibres. 


















TIMBER. 


221 


Similarly, if disk No. 2 is cut up as in the figure, the specific weight of 
the different pieces is: 

a about 0.52 
b about 0.64 
c about 0.67 
d , e, f about 0.65 

Showing that in this disk, at least, the wood formed during the many years’ 
growth, represented in piece a , is much lighter than that of former years. 
It also shows that the best wood is the middle part, with its large proportion 
of dark summer-wood bands. 

Cutting up all disks in the same way, it will be found that the piece a 
of the first disk is heavier than piece a of the fifth, and that piece c of the 
first disk excels the piece c of all the other disks. This shows that the wood 
grown during the same number of years is lighter in the upper parts of the 
stem; and if the disks are smoothed on their radial surfaces and set up one 
on top of the other in their regular order for sake of comparison, this decrease 
in weight will be seen to be accompanied by a 
decrease in the amount of summer wood. The 
color effect of the upper disks is conspicuously 
lighter. 

If our old pine had been cut one hundred 
and fifty years ago, before the outer, lighter wood I 
was laid on, it is evident that the weight of the wood! 
of any one disk would have been found to increase 
from the centre outward, and no subsequent decrease 
could have been observed. 

In a thrifty young pine, then, the wood is heav¬ 
ier from the centre outward, and lighter from below 



disc h 


disc 3 


disc 3 


I 


disc 1 


Fig. 98. —Location of 
Wood Samples. 


upward; only the wood laid on in old age fails in weight below the 
average. The number of brownish bands of summer wood are a direct indi¬ 
cation of these differences. 

if an old oak is cut up in the same manner, the butt cut is also found 
heaviest and the top lightest, but, unlike the disk of pine, the disk of oak has 
its firmest wood at the centre, and each successive piece from the centre out¬ 
ward is lighter than its inner neighbor. 

Examining the pieces, this difference is not as readily explained by the 
appearance of each piece as in the case of pine wood. Nevertheless, one con¬ 
spicuous point appears at once: the pores, so very distinct in oak, are very 
minute in the wood near the centre and thus the wood is far less porous. 
Studying different trees it is found that, in the pines, wood with narrow 
rings is just as heavy as, and often heavier than, the wood with wider rings, 
but if the rings are unusually narrow in any part of the disk the wood has 
alio-hter color; that is, there is less summer wood and therefore less weight. 

In oak, ash’, or elm trees of thrifty growth, the wider rings (not less than 










222 


THE MATERIALS OF CONSTRUCTION ,. 


one-twelfth inch) always form the heaviest wood, while any piece with very 
narrow rings is light. On the other hand, the weight of a piece of hard 
maple or birch is quite independent of the width of its rings, since the 
structure here is uniform across the entire width of the annual ring. 

The bases of limbs (knots) are usually heavy, very heavy in conifers, and 
also the wood which surrounds them, but generally the wood of the limbs is 
lighter than that of the stem, and the wood of the roots is the lightest. 

191. Weight of Different Species.—In general, it may be said that none 
of the native woods in common use in this country are, when dry, as heavy 
as water, i.e., 62 pounds to the cubic foot. Few exceed 50 pounds, while 
most of them fall below 40 pounds, and much of the pine and other conif¬ 
erous wood weighs less than 30 pounds per cubic foot. 

The weight of the wood is, in itself, an important quality. Weight assists 
in distinguishing maple from poplar. Lightness, coupled with great strength 
and stiffness, recommends wood for a thousand different uses. To a large 
extent weight predicates the strength of the wood, at least in the same species, 
so that a heavy piece of oak will exceed in strength a light piece of the same 
species, and in pine it appears probaMe that, weight for weight, the strength 
of the wood of various pines is nearly equal, all being reduced to the same 
dryness. See Art. 443, p. 667. 

WEIGHT OF KILN-DRIED WOOD OF DIFFERENT SPECIES. 


Approximate. 


Common Name of Species. 


Weight of— 

■ 

Specific 

Gravity. 

1 cubic 
foot. 

1000 feet 
of lum¬ 
ber. 

{a) Very heavy woods: 

* Hickory, oak, persimmon, osage orange, black locust, 
hackberry, blue beech, best of elm, and ash. 

0.70-0.80 

Pounds. 

42-48 

Pounds. 

3700 

( b) Heavy woods: 

Asli, elm, cherry, birch, maple, beech, walnut, sour gum, 
coffee-tree, honey-locust, best of Southern pine, and 
tamarack. . 

.60- 70 

36-42 

3200 

(c) Woods of medium weight : 

Southern pine, pitch-pine, tamarack, Douglas spruce, 
Western hemlock, sweet gum, soft maple, sycamore, 
sassafras, mulberry, light grades of birch and cherry.. 

.50- .60 

30-36 

2700 

(cl) Light woods: 

Norway and bull pine, red cedar, cypress, hemlock, the 
heavier spruce and fir, redwood, basswood, chestnut, 
but ternut, tillip.catalpa, buckeye,heavier grades of poplar 

o 

1 

Or 

O 

24-30 

2200 

( e ) Very light woods : 

White pine, spruce, fir, white cedar, poplar. 

05 

o 

1 

o 

18-24 

1800 


* For the scientific names of timbers see the list of Useful American Timbers at the 
end of this chapter. 






















TIMBER. 


223 


Since ordinary lumber contains knots and also more water than is here 
assumed, and also since its dimensions either exceed or fall short of perfect 
measurement, the figures in the table are only approximate. 

Thus 1000 feet, B. M., of long-leaf pine weighs: 

Pounds. 


Rough and green.4500 

Boards rough but seasoned.3500 

Boards dressed and seasoned.3000 

Flooring, matched dressed and seasoned.2500 

Weather-boarding, bevelled and dressed.1500 


MOISTURE IN WOOD. 

192. Moisture Distribution.—Water may occur in wood in three con¬ 
ditions: (l) it forms the greater part (over 90 per cent) of the proto¬ 
plasmic contents of the living cells; (2) it saturates the walls of all 

cells; and (3) it entirely or at least partly fills the cavities of the life¬ 
less cells, fibres, and vessels. In the sapwood of pine it occurs in all 

three forms; in the heartwood only in the second form, that is, it 

merely saturates the walls. Of 100 pounds of water associated with 
100 pounds of dry wood-substance in 200 pounds of fresh sapwood of 
white pine, about 35 pounds are needed to saturate the cell walls, 
less than 5 pounds are contained in living cells, and the remaining GO 
pounds partly fill the cavities of the wood-fibres. This latter forms the 
sap as ordinarily understood. It is water brought from the soil, containing 
small quantities of mineral salts, and in certain species (maple, birch, etc.) 
it also contains at certain times a small percentage of sugar and other 
organic matter. These organic substances are the dissolved reserve food 
stored during winter in the pith-rays, etc., of the wood and bark; generally 
but a mere trace of them is to be found. From this it appears that the 
solids contained in the sap, such as albumen, gum, sugar, etc., cannot 
exercise the influence on the strength of the wood which is so common^ 
claimed for them. 

The wood next to the bark contains the most water. In the species 
which do not form heartwood the decrease toward the pith is gradual; but 
where this is formed, the change from a more moist to a drier condition is 
usually quite abrupt at the sapwood limit. In long-leaf pine the wood of 
the outer 1 inch of a disk may contain 50 pel cent of \\ater, that of the 
next or second inch, only 35 per cent, and that of the heartwood only 20 
per cent. In such a tree the amount of water in an entire cross-section 
varies with the amount of sapwood, and is therefore greater for the upper 
than the lower cuts, greater for limbs than stems, and greatest of all in the 
roots. 

Different trees, even of the same kind and from the same place, differ 
as to the amount of water they contain. A thrifty tree contains more water 







224 


TUE MATERIALS OF CONSTRUCTION. 


than a stunted one, and a young tree more than an old one, while the wood 
of all trees varies in its moisture relations with the season of the year. 

Contrary to the general belief, a tree contains about as much water in 
winter as in summer. The fact that the bark peels easily in the spring 
depends on the presence of incomplete, soft tissue, the rapidly growing 
cambium layer found between wood and bark during this season, and has 
little to do with the total amount of water contained in the wood of the 
stem. 

Even in the living tree a flow of sap from a cut occurs only in certain 
kinds of trees and under special circumstances; from boards, timber, etc., 
the water does not flow out, as is sometimes believed, but must be evapo¬ 
rated.* 

193. Drying Timber.—The rapidity with which water is evaporated, 
that is, the rate of drying, depends on the size and shape of the piece and 
on the structure of the wood. An inch board dries more than four times 
as fast as a 4-inch plank and more than twenty times as fast as a 10-incli 
timber. White pine dries faster than oak. A very moist piece of pine or 
oak will, during one hour, lose more than four times as much water per 
square inch from the cross-section, but only one half as much from the 
tangential as from the radial section. 

In a long timber, where the end or cross-sections form •but a small part 
of the drying surface, this difference is not so evident. Nevertheless, the 
ends dry and shrink first, and being opposed in this shrinking by the more 
moist adjoining parts they check, the cracks largely disappearing as season¬ 
ing progresses. 

High temperatures are very effective in evaporating the water from 
wood no matter how humid the air. A fresh piece of sap wood may lose 
weight in boiling water, and can be dried to quite an extent in hot steam. 

Kept on a shelf in an ordinary dwelling, wood still retains 8 to 10 per 
cent of its weight of water, and this percentage is always greater than the 
percentage of moisture in the surrounding air. Nor is the amount of 
water in dry wood constant; the weight of a panful of shavings varies 
with the time of day, being on a summer day greatest in the morning and 
least in the afternoon. 

Desiccating the air with chemicals will cause the wood to dry, but wood 
thus dried at 80° F. will still lose water in the kiln. Wood dried at 120° 
F. loses water still if dried at 200° F., and this again will lose more water 
if the temperature is raised. Absolutely dry wood cannot be obtained; 
chemical destruction sets in before all the water is driven off. 

On removal from the kiln the wood at once takes up water from the air, 

* The seeming exceptions to this rule are mostly referable to two causes, namely : 
(a) Clefts or “ shakes ” will allow water contained in them to flow out. ( b) From 
sound wood, if very sappy, water is forced out whenever the wood is warmed, just as 
water flows from green wood in the stove. 





TIMBER. 


225 


even in the driest weather. At first the absorption is quite rapid; at the 
end of a week a short piece of pine, lb inches thick, has regained two 
thirds of, and in a few months all, the moisture which it had when air-dry, 
8 to 10 per cent, and also its former dimensions. 

In thin boards all parts soon attain the same degree of dryness; in 
heavy timbers the interior remains moister for many months, and even 
years, than the exterior parts. Finally an equilibrium is reached, and then 
only the outer parts change with the weather. 

With kiln-dried wood all parts are equally dry, and when exposed the 
moisture coming from the air must pass in through the outer parts, and 
thus the order is reversed. Timber seasoned out of doors requires months, 
or even years, before it is at its best; kiln-dry timber, if properly handled, 
is prime at once. 

Dry wood when soaked in water soon regains its original volume, and 
in the heartwood portion it may even surpass it; that is to say, swell to a 
larger dimension than it had when green. With the soaking it continues 
to increase in weight, the cell-cavities filling with water, and if left many 
months all pieces sink. Yet even after a year's immersion a piece of oak 
2 by 2 inches and only G inches long still contains air, i.e., it has not 
taken up all the water it can. By rafting, or prolonged immersion, wood 
loses some of its weight, soluble materials being leached out, but it is not 
impaired either as fuel or as building material. Immersion and, still more, 
boiling and steaming reduce the hygroscopicity of wood and, therefore, also 
the troublesome “ working,” or shrinking and swelling. 

Exposure in dry air to a temperature of 300° F. for a short time re¬ 
duces, but does not destroy, the hygroscopicity and with it the tendency to 
shrink and swell. A piece of red oak which has been subjected to a tem¬ 
perature of over 300° F. still swells in hot water and shrinks in the kiln. 

In artificial drying, temperatures of from 158° to 180° F. are usually 
employed. Pine, spruce, cypress, cedar, etc., are dried fresh from the saw, 
allowing four days for 1-inch boards; hard woods, especially oak, ash, 
maple, birch, sycamore, etc., are air-seasoned for three to six months, to 
allow the first shrinkage to take place more gradually, and are then exposed 
to the above temperatures in the kiln for about six to ten days for 1-inch 
lumber. Freshly cut poplar and cottonwood are often dried directly in 

kilns. 

By employing lower temperatures, 100° to 120° F., green oak, ash, etc., 
can be seasoned in dry kilns without danger to the material.* Steaming 
the lumber is commonly resorted to in order to prevent checking and 
“ casehardening,” but not, as has frequently been asserted, to enable the 
board to dry. Yard-dried lumber is not dry, and its moisture is too un- 


* The dry kiln shown in Fig. 99 is operated at this temperature, and live steam is 
admitted once or twice a day to prevent checking.—J. B. J. 





226 


THE MATERIALS OF CONSTRUCTION. 


evenly distributed to insure good behavior after manufacture. Careful 
piling of the lumber both in the yard and kiln, is essential to good drying. 



Piling boards on edge or standing them on end is believed to hasten drying. 
This is true only because in either case the air can circulate more freely 
around them than when they are piled in the ordinary way. Boards on 




























































































































































































































TIMBER. 


227 


end dry unequally; the upper half dries much faster than the lower half 
and horizontal piling is, therefore, preferable. 

Since the proportion of sap- and heart-wood varies with size, age, species, 
and individual, the following figures must be regarded as mere approxima¬ 
tions: 


POUNDS OF WATER LOST IN DRYING 100 POUNDS OF GREEN WOOD 

IN THE KILN. 

Common Names of Species. 

Sapwood or 
Outer Part. 

Heartwood 
or Interior. 

(1) Pines, cedars, spruces, and firs. 

(2) Ovoress extremelv variable. 

45-65 

50-65 

60-65 

40-50 

16-25 

18-60 

40-60 

30-40 

(3) Poplar, cottonwood, basswood. 

(4) Oak, beech, ash, elm, maple, birch, hickory, chestnut, wal¬ 

nut and sveamore. 



The lighter kinds have the most water in the sapwood; thus sycamore has more than 

hickory. 



SHRINKAGE OF WOOD. 


BUS 


194. Shrinkage Explained.—When a short piece of wood-fibre, such as 
that shown in Fig. 100, A , is dried it shrinks, its wall grows thinner (as in¬ 
dicated by dotted lines), its width, ab, 
the thickness of the fibre, becomes 
smaller, and the cavity or opening 
larger, but, strange to say, the height 
or length, be, remains the same. In a 
similar piece of fibre with a thinner 
wall (Fig. 100, B) the effect is the 
same, but the wall being only half as 
thick the total change is only about 



TDTniiiiB. 


B 


half as great.* 


If sections or pieces of fibres are 
dried and then placed on moist blotting- 
paper, they will take up water and 
swell to their original size, though the 
water has been taken up only by their 
walls and none has entered into their 
openings or lumina. r J his indicates 
that the water in the cavity or lumen of 
a fibre has nothing to do with its di¬ 
mensions, and that if the cell-walls are saturated it makes no difference 


m 


Fig. 100.—Short Pieces of Wood-fibres, 
one thick-, the other thin-walled; mag¬ 
nified. 


* Though generally true, it must not be supposed that the fibres of all species, or 
even the fibres of the same tree, shrink exactly in proportion to the thickness of theii 

walls. 























































































































228 


TI1E MATERIALS OF CONSTRUCTION. 


in the volume of a block of pine wood whether the cell-cavities are empty 
as in the heartwood or three fourths filled as in the sapwood. 

If an entire fibre, as shown in Fig. 101, is dried, the wall at its ends 
a and b, like those of the sides, grows thinner, and thereby the length of 
the entire cell grows shorter. Since this length is often a hundred or 
more times as great as the diameter, the effect of this shrinkage is inap¬ 
preciable; and if a long board shrinks lengthwise, it is largely due, as 
we shall see, to quite another cause. 

A thin cross-section of several fibres (see Fig. 102, A) like the piece 
of a single fibre shrinks when dried, the wall of each fibre becomes 



b 


Fig. 101. 
Isolated Cell. 



Fig. 10 '?.—Warping of 
Wood. 


thinner, and thus each piece smaller, and the piece on the whole necessarily 
shares this diminution of size, the distances ab and cd each becoming- 
shorter. Where the cells are very similar in size and in the thickness of 
their walls, as in the case of piece A, Fig. 102, ab and cd become shorter 
by about the same amount; but if the piece is made up of fibres some 
of which have thin and others thick walls, as piece B, Fig. 102, then, the 
row of thick-walled cells shrinking much more than the row of thin-walled 
cells, the piece becomes unevenly shrunk or warped as shown in Fig. 102, 
C. Not only is the piece warped, but the force which led to this warping 
continues to strain the interior parts of the piece in different directions. 

Since in all our woods cells with thick walls and cells with thin walls 
are more or less intermixed, and especially as the spring wood and summer 
wood nearly always differ from each other in this respect, strains and 
tendencies to warp are always active when wood dries out, because the 
summer wood shrinks more than the spring wood, heavier wood in general 
more than light wood of the same kind. 







































TIMBER 


229 



X 



If the piece A, Fig. 102, after drying is placed edgewise on moist blot¬ 
ting-paper, the cells on the under side, at cd, take up moisture from the 
paper and swell before the upper cells at ab re¬ 
ceive any moisture. This causes the under side 
of the piece to become longer than the upper 
side, and, as in the case of piece C, warping c .^ 
occurs. Soon, however, the moisture penetrates 
to all the cells and the-piece straightens out. A 
thin board behaves exactly like this minute 
piece, only the process is slower and more easily 
observed. But while a thin board of pine curves 
laterally, it remains quite straight lengthwise, 
since in this direction both shrinkage and swell¬ 
ing are small. A thin disk or cross-section 
swells, and when moistened on one side warps as 
readily in one direction as in another. If a green 
board is exposed to the sun upon one side, warp¬ 
ing is produced by removal of water and conse¬ 
quent shrinkage of that side, and the course of 
the process is simply reversed. 

As already stated, wood loses water faster 
from the end than from the longitudinal faces. 

Hence the ends shrink at a different rate from 
the interior parts. 

195. Effects of Shrinkage.—In a timber, the width AB (Fig. 103, A’) 
may have shortened (Fig. 103, Y), while a short distance from the end cd 
the original width is still preserved. This should produce a bending of 
the parts toward the centre of the piece as shown in exaggeration at Y, but 
the rigidity of the several parts of the timber prevents such bending and 
the consequent strain leads to their separation as shown at Z, the end sur¬ 
face of the timber being “ checked.” 

As the timber dries out, the line cd becomes shorter, the parts 1 to G 
are allowed to approach again, and the checks close up and are no longer 



103.—Formation 
Checks. 


visible. 

The faster the drying at the surface, the greater is the difference in the 
moisture of the different parts, and hence the greater the strains and con¬ 
sequently also the amount of checking. This becomes very evident when 
fresh wood is placed in the sun, and still more in a hot kiln. While most 
of these smaller checks are thus only temporary, closing up again, some 
large radial checks remain and even grow larger as drying progresses. 
Their cause is a different one and will presently be explained. 

The temporary checks not only occur at the ends, but are developed oil 
the sides also, only to a much smaller degree. They become especinlly an- 

















































230 


THE MATERIALS OF CONSTRUCTION. 


planks of hard woods, and also on peeled 
logs when exposed to the sun. 

So far we have considered the wood 
as if made np only of parallel fibres all 
placed longitudinally in the log. This, 
however, is not the case. A large part of 
the wood is formed by the medullary or 
pith rays. In pine over 15,000 of these 
occur on a square inch of a tangential sec- 
tion, and even in oak the very large rays, 
which are readily visible to the eye, repre¬ 
sent scarcely a hundredth part of the num¬ 
ber which the microscope reveals. 

As seen in Fig. 104, the cells of these 
rays have their length at right angles to 
the direction of the wood-fibres. 

If a large pith-ray of white oak is 
whittled out and allowed to dry, it is 
found to shrink greatly in the direction 
from c to cl (Fig. 104), while, as we have 
stated, the fibres to which the ray is 
firmly grown in the wood do not shrink in the same direction. There¬ 
fore, in the wood, as the cells of the pith-ray dry, they pull on the longitu¬ 
dinal fibres and try to shorten them, and, being opposed by the rigidity of 
the fibres, the pith-ray is greatly strained. But this is not the only strain 
it has to bear. Since the fibers from a to b (Fig. 104) shrink as much 
again as the pith-ray in this, its longitudinal direction, the fibres tend to 
shorten the ray, and the latter, in opposing this, prevents the former from 
shrinking as much as they otherwise would. Thus the structure is sub¬ 
jected to severe strains at right angles to each other; and herein lies the 
greatest difficulty of wood-seasoning, for whenever the wood dries rapidly 
these fibres have not the chance to “give” or accommodate themselves, 
and hence fibres and pith-rays separate and checks result which, whether 
visible or not, are detrimental in the use of the wood. 

The contraction of the pith-rays parallel to the length of the board is 
probably one of the causes of the small amount of longitudinal shrinkage 
which has been observed in boards A' The smaller shrinkage of the pith- 
rays along the radius of the log (the length of the pith-ray) opposing the 
shrinkage of the fibres in this direction becomes one of the causes of the 
second great trouble in wood-seasoning, namely, the difference in the 


noying on the surface of thick 



Fig. 104.—Small Pith-ray in Oak. a, 
b, wood-fibres; c, d, cells of pith- 
ray. 


* In addition to this all fibres having an oblique position, as those at pith-rays and 
knots, also the oblique, tapering ends of all fibers, contribute to this longitudinal shrink¬ 
age, since one component of their normal shrinkage is longitudinal. 








































































TIMBER. 


231 


amount of the shrinkage along the radius and that along the rings or 
tangent. 

This greater tangential shrinkage appears to be due, 
in part, to the cause just mentioned, but also to the fact 
that the greatly shrinking bands of summer wood are 
interrupted, along the radius, by as many bands of porous 
spring wood, while they are continuous in the tangential 
direction. In this direction, therefore, each such band 
tends to shrink, as if the entire piece were composed of 
summer wood : and since the summer wood represents the 
greater part of the wood-substance, this tendency of 
greater tangential shrinkage prevails. 

The effect of this greater tangential shrinkage affects 
every phase of woodworking. It leads to permanent 
checks, and causes the log to split open on drying. 

Sawed in two, the flat sides of the log become convex, 
as in Fig. 105; sawed into a timber, it checks along the 
median line of the four faces, and if converted into 
boards the latter take on the forms shown in Fig. 105, 
all owing to the greater tangential shrinkage of the wood. Fl(} \ Effects 

Briefly, then, shrinkage of wood is due to the fact 
that the cell-walls grow thinner on drying. The thicker cell-walls and there¬ 
fore the heavier wood shrinks most, while the water in the cell-cavities does 
not influence the volume of the wood. Owing to the great difference of 
cells in shape, size, and thickness of walls, and still more in their arrange¬ 
ment, shrinkage is not uniform in any kind of wood. This irregular defor¬ 
mation produces stresses which grow with the difference between adjoining 
cells and are greatest at the pith-rays. These deformations cause warping 
and checking, and exist even when no outward signs are visible; they are 
greater if the wood is dried rapidly than if dried slowly, but can never be 
entirely avoided. 

Temporary checks are caused by the more rapid drying of the outer parts 
of any stick; permanent checks are due to the greater shrinkage, tangen¬ 
tially, along the rings than that along the radius. This, too, is the cause of 
most of the ordinary phenomena of shrinkage, such as the difference in 
behavior of entire and quartered logs, “bastard” (tangent) and “rift” 
(radial) boards, etc., and explains many of the phenomena erroneously attrib¬ 
uted to the influence of the bark, or of the greater shrinkage of outer and 
inner parts of any log. 

Once dry, wood may be swelled again to its original size by soaking in 
water, boiling, or steaming. Soaked pieces, on drying, shrink again as 
before; boiled and steamed pieces do the same, but to a slightly less degree. 
Neither hygroscopicity, i.e., the capacity of taking up water, nor shrinkage of 
m>od can be overcome by drying at temperatures below 200° F. Higher 













232 


THE MATERIALS OF CONSTRUCTION. 


temperatures, however, reduce these qualities, but nothing short of a coaling- 

heat robs wood of the capacity to shrink and 
swell. Rapidly dried in the kiln, the wood of 
oak and other hard woods “ caseharden,” that 
is, the outer part dries and shrinks before the 



interior has a chance to do the same, and thus 


Fig. 106. — “ Honeycombed 
Board. The checks or cracks 
form along the pith-rays. 


forms a firm shell or case of shrunken, com¬ 
monly checked wood around the interior. This 
shell does not prevent the interior from dry¬ 
ing, but when this drying occurs, the interior is commonly checked along 
the medullary rays, as shown in Fig. 106. In practice this occurrence can be 
prevented by steaming the lumber in the kiln, and still better by drying the 
wood in the open air or in a shed before placing in the kiln. Since only 
the first shrinking is apt to check the wood, any kind of lumber which has. 
once been air dried (three to six months for 1-inch stuff) may be subjected 
to kiln-heat without any danger. Kept in a bent or warped condition during 
the first shrinking, the wood retains the shape to which it was bent and 
firmly opposes any attempt at subsequent straightening. 

196. Amount of Shrinkage in Timber.—Sapwood, as a rule, shrinks more 
than heart wood of the same weight, but very heavy heart wood may shrink 
more than lighter sapwood. The amount of water in wood is no criterion of 
its shrinkage, since in wet wood most of the water is held in the cavities, 
where it has no effect on the volume. 

The wood of pine, spruce, cypress, etc., with its very regular structure, dries 
and shrinks evenly and suffers much less in seasoning than the wood of 
broad-leaved trees. Among the latter, oak is the most difficult to dry with¬ 
out injury. Small-sized split ware and “rift” boards season better than 
ordinary boards and planks. 

To avoid “working” or warping and checking, all high-grade stock is 
carefully seasoned, preferably in a kiln, before manufacture. Thicker pieces 
may be made of several parts glued together; larger surfaces are made in 
panels or of smaller pieces covered with veneer. Boring is sometimes resorted 
to to prevent the checking of wooden columns. 

Since repeated swelling increases the injuries due to seasoning, wood 
should be protected against moisture when once it is dry. 

Since tfie shrinkage of our woods has never been carefully studied, and 
since wood, even from the same tree, varies within considerable limits, the- 
figures given in the following table are to be regarded as mere approximations. 
The shrinkage along the radius and that along the tangent (parallel to the 
rings) are not stated separately in the following table, and the figures repre¬ 
sent an average of the shrinkage in the two directions. Thus, if the shrink¬ 
age of soft pine is given at 3 inches per hundred, it means that the sum of 
radial and tangential shrinkage is about 6 inches, of which about 4 inches fall 






TIMBER. 


233 


to the tangent and 2 inches to the radius, the ratio between these varying 
from 3 to 2, a ratio which practically prevails in most of our woods. 

Since only an insignificant longitudinal shrinkage takes place (being 
commonly less than 0.1 inch per hundred, though in oak it is much more), the 
change in volume during drying is about equal to the sum of the radial and 
tangential shrinkage, or twice the amount of linear shrinkage indicated in 
the table. 

Thus, if the linear average shrinkage of soft pine is 3 inches per hun¬ 
dred, the shrinkage in volume is about 6 cubic inches for each 100 cubic 
inches of fresh wood, or 6 per cent of the volume. 

APPROXIMATE SHRINKAGE OF A BOARD, OR SET OF BOARDS, 100 INCHES 


WIDE, DRYING IN THE OPEN AIR. 

Lateral 

Common Names of Species. Shrinkage' 

Inches. 

(1) All light conifers (soft pine, spruce, cedar, cypress). 3 

(2) Heavy conifers (hard pine, tamarack, yew), honey-locust, box-elder, wood 

of old oaks. 4 

(8) Ash, elm, walnut, poplar, maple, beech, sycamore, cherry, black locust.. 5 

(4) Basswood, birch, chestnut, horse chestnut, blue beech, young locust. 6 

(5) Hickory, young oak, especially red oak... Up to 10 


MECHANICAL PROPERTIES OF WOOD.* 

197. General View.—Every joist and studding, every rafter, sash, and 
door, the chair we sit on, the floor we walk on, the wood of the wagon or 
boat we ride in, are all continually tested as to their stiffness and strength, 
their hardness and toughness. Every step from the simple splitting of a 
shingle or stave to the construction of the most elegant carriage or side¬ 
board involves a knowledge not only of one, but of several, of the mechani¬ 
cal properties of the material. 

In the shop the fitness of the wood for a given purpose never depends on 
any one quality alone, but invariably upon a combination of several quali¬ 
ties. A spoke must not only be strong, it must be stiff to hold its shape, it 
must be tough to avoid shattering to pieces, and it must also be hard or else 
its tenons will become loose in their mortises. 

Selecting wood in this way, the woodworker has learned almost all that 
is at present known about his material; but in many cases the great diffi¬ 
culty which always attends the judgment of complex phenomena has led to 
erroneous conclusions, and not a few well-established beliefs have their origin 
more in accidental errors of observation than in fact. 

The experimenter endeavors to avoid this complexity by testing the 

* This section of the Bulletin was made very simple for popular comprehension. 
See Chap. XXXII. p. 664 for results of the U. S. Timber Tests conducted by the 
author.—J. B. J. 









234 


THE MATERIALS OF CONSTRUCTION. 


wood for each kind of resistance separately; when tested as to their stiff¬ 
ness, the pieces are all shaped, placed, and loaded alike. The wood is 
selected with a definite object in view; it is green or dry, clear or knotty, 
straight or cross-grained, according as he wishes to find out the influence of 
each of these conditions. If pine and oak are to be compared, the pieces 
are from the same position in the tree and are tried under exactly the same 
conditions, and thus the case is simplified. 

But even results thus arrived at cannot be used indiscriminately, and 
the figures on the strength of oak given in any book must not be supposed 
to apply to all oak if tested in the given manner. This is due to the fact 
that a piece of wood is not simply a material but a structure, just as much 
as a railroad-bridge or a balloon frame, and as such varies greatly even in 
the wood of the same tree, nay, more than that, even in the same year’s 
growth of the same cross-section of a log. 

A scantling resists bending; it is stiff. On removal of the load it 
straightens; it is elastic. A column, a prop, or the spoke of a wagon-wheel 
resists being crushed endwise. So does the upper side of a joist or beam 
when loaded, while the under side of the beam or of an axe-handle suffers in 
tension. The tenons of a window sash or of a door tend to break out their 
mortises, the wood has to resist shearing along the fibres; the steel edge of 
the eye tends to cut into the hammer-handle, it tries to shear it across the 
grain, and every nail, screw, bore-hole, or mortise tends to split the board 
and tries the wood as to its cleavability, while all “bent” ware, from the 
wicker basket to the one-piece felly or ship’s knee, involves its flexibility. 

198. Stiffness.—If 100 pounds placed in the middle of a stick 2 by 2 
inches and 4 feet long, supported at both ends, bend or “ deflect ” this 
stick one eighth of an inch (in the middle), then 200 pounds will bend it 
about one-fourth inch, 300 pounds three-eighths inch, the deflection varying 
directly as the load. Soon, however, a point is reached where an additional 
100 pounds adds more than one-eighth inch to the deflection—the limit of 
elasticity has been reached. Taking another piece from the straight-grained 
and perfectly clear plank of the same depth and width, but 8 feet long, the 
load of 100 pounds will cause it to bend not only one-eighth inch, but will 
deflect it by about 1 inch. Doubling the length reduces the stiffness eight¬ 
fold. Stiffness then decreases as the cube of the length. 

Cutting out a piece 2 by 4 inches and 4 feet long, placing it flatwise so 
that it is double the width of the former stick, and loading it with 100 
pounds, we find it bending only one-sixteenth inch: doubling the width 
doubles the stiffness. 

Setting the same 2 X 4-inch piece on edge, so that it is 2 inches wide 
and 4 inches deep, the load of 100 pounds bends it only about one sixty- 
fourth inch: doubling the thickness increases the stiffness about eightfold. 

It follows that if we double the length and wish to retain the same 
stiffness we must also double the thickness of the piece. 


TIMBER. 


235 


A piece of wood is usually stiffer with the annual rings set vertically 
than if the rings are placed horizontally to the load. 

Cross-grained and knotty wood, to be sure, is not as stiff as clear lumber; 
a knot on the upper side of a joist, which must resist in compression, is, 
however, not so detrimental as a knot on 
the lower side, where it is tried in tension. 

Every large timber which comes from A 
the central part of the tree contains knots, L 
and much of its wood is cut more or less 
obliquely across the grain, both conditions 


-- 1 —— — 

/ - - - \d 


i 

i 

— f- 
/ 

/ 

/ 

/ 

• 

t _ 

i 

— ; 





Fig. 107.—Bending a Beam. 


rendering such material comparatively less stiff than small clear pieces. 

The same stick of pine green or wet is only about two thirds as stiff as 
when dry. A heavy piece of long-leaf pine is stiffer than a light piece; 
heavy pine in general is stiffer than light pine, but a piece of hickory, 
although heavier than the pine, may not be as stiff as the piece of long-leaf 
pine; and a good piece of larch exceeds in stiffness any oak of the same 
weight. 

In the same tree stiffness varies with the weight, the heavier wood being 
the stiffer; thus the heavier wood of the butt log is stiffer than that of the 
top; timber with much of the heavy summer wood is stiffer than timber of 
the same kind with less summer wood. In old trees (of pine) the centre of 
the tree and the sap are the least stiff; in thrifty young pine the centre is 
the least stiff, but in young second-growth hard woods it is the stiffest. 

Since it is desirable, and for many purposes essential, to know before¬ 
hand that a given piece with a given load will bend only a given amount, 
the stiffness of wood is usually stated in a uniform manner and under the 
term “ modulus (measure) of elasticity.” 

If AB, Fig. 107, is a piece of wood, and cl the deflection produced by a 
we ight or load, the stiffness of the wood, as usually stated, is foiftid by the 
formula 

wr 

Modulus of elasticity — E — 


where IT is the weight, l the length, l and h the breadth and depth (height) 
of the stick, and d the deflection for the load W In the following table 
the woods are grouped according to their stiffness. The figures are only 
rough approximations which are based on the data given in Vol. IX of the 
Tenth Census. The first column contains the above modulus, the second 
shows how many pounds will produce a deflection of 1 inch in a stick 1 by 1 
by 12 inches, assuming that it could endure such bending within the limits 
of elasticity, and the third column gives the number of pounds which will 
bend a stick 2 by 2 inches and 10 feet long through 1 inch. 

The stick is assumed to rest on both ends; if it is a cantilever, i.e, fas¬ 
tened at one end and loaded at the other, it bears but half as much load 
at its end for the same deflection. 






236 


TEE MATERIALS OF CONSTRUCTION. 


From the third column it is easy to find how many pounds would bend 
a piece of the same kind of other dimensions. A 2 X 4-inch bears eight, 
a 2 X 6-inch twenty-seven times as much as the 2 X 2-inch; a piece 8 feet 
long is about twice as stiff as a 10-foot piece; apiece 12 feet only about 
three fifths, 14 feet one third, 16 feet two ninths, 18 feet one sixth, and 20 


feet one eighth as stiff. 

The number of pounds which will bend any piece of sawed timber by 1 
inch may be found by using the formula 


Necessary weight = 


4 Ebld 

r ’ 


where E is the figure in the first column, and b, h, l, the breadth, deptn, and 
length of the timber in inches. If the deflection is not to exceed one-half 
inch, only one half this load, and if one-fourth inch, only one fourth this load * 

is permissible; or, in general, W — ——, where d is the deflection in inches.. 


TABLE OF STIFFNESS (MODULUS OF ELASTICITY) OF DftY WOOD. 

GENERAL AVERAGES. 


Species. 

Modulus of 
Elasticity 

„ wi 3 

Approximate Weight 
which deflects by 
Inch a Piece 

4dbh 3 
per Square 
Inch. 

1 by 1 Inch 
and 

12 In. long. 

2 by 2 In. 
and 

10 Ft. long. 

(1) Live oak, good tamarack, long-leaf, Cuban, and short- 
leaf pine, good Douglas spruce,'Western hemlock, 
yellow and cherry birch, hard maple, beech, locust, 

Pounds. 

Pounds. 

Pounds. 

and the best of oak and hickory. 

1,680,000 

3,900 

62 

(2) Birch, common oak, hickory, white and black spruce, 
loblolly and red pine, cypress, best of ash, elm, and 

• 


poplar and black walnut. 

(3) Maples, cherry, ash, elm, sycamore, sweet gum, but¬ 
ternut. poplar, basswood, white, sugar, and bull 

1,400,000 

3,200 

51 

pine, cedars, scrub pine, hemlock, and fir. 

(4) Box-elder, horse-chestnut, a number of Western soft 

1,100,000 

2,500 

40 

pines, inferior grades of hard woods. 

1,000,000 

2,300 

37 


199. Cross-breaking or Bending Strength.—When the addition of 100 
pounds to the load on our 2 X 2-inch piece begins to add more than one 
eighth incfi to the deflection, that is, when the stick has been bent beyond 
its “elastic limit,” it still requires an increase of 30 to 50 per cent to the 
load before the stick breaks. The load which is borne before the limit of 
elasticity is reached indicates the strength of the wood up to this important 
point; the load which causes it to break represents its absolute strength, or 
the “ cross-breaking or bending strength” as it is commonly called. 

In long-leaf pine the former (modulus of strength at the elastic limit)* 


* The “elastic limit” in this case is somewhat of an arbitrary quantity, namely, the 
point where 100 pounds produces a deflection 50 per cent greater than the first 100 
pounds. See Art. 13, p. 18, and Arts. 261-263, pp. 306-311. 























TIMBER. 


237 


is commonly about three fourths of the latter. If left loaded for a consid- 
time, a load even less than that which brings the stick to its elastic limit 
will cause it to break, and this load should therefore not be reached in prac¬ 
tice. 

Unlike the stiffness, the strength of a timber varies approximately with 
the squares of the thickness and decreases directly with increasing length and 
not with the cube of this latter dimension. Thus if our piece 2 by 2 inches 
and 4 feet long can bear 1000 pounds before it breaks, a 2 X 4-inch laid 
flat will break with about 2000 pounds, and if set edgewise it requires about 
4000 pounds to break it, while a piece of the same kind 2 by 2 inches and 
double the length (8 feet) breaks with half the original load, or only 500 
pounds. 

All conditions of the material which influence the stiffness also influ¬ 
ence the bending strength. Seasoning increases, moisture decreases, the 
strength; knots and cross-grain depress it, and both are more dangerous on 
the lower than on the upper side. But while the conifers with their sim¬ 
ple cell-structure excel in stiffness, the better hard woods develop the 
greater strength in bending. Like elasticity and stiffness, the strength is 
expressed in a uniform manner by the so-called “ modulus of rupture,” to 
permit ready estimation of the strength of any given piece. This modulus 
refers to the resistance per square inch which the parts most strained, “ the 
extreme fibre,” offer. The figures usually tabulated are obtained by the 
formula 

3 Wl 

Strength per square inch of extreme fibre = / = > 

where W is the breaking-load, l the length, b and h the breadth and depth 
of the tested piece of wood. 

The following table presents our common woods grouped as to their 
strength in bending. The load, as before, is supposed to act altogether in 
the middle. Column 1 gives the strength of the extreme fibre, as explained 
above; column 2, the number of pounds which will break a piece 1 by 1 inch 
and 12 inches long; and column 3, the strength of a stick 2 by 2 inches and 
10 feet long: from which the strength of any given piece can readily be esti¬ 
mated, allowing, however, for defects, which increase with the size. Thus, 
if a good piece of pine 2 by 2 inches and 10 feet long breaks with 400 pounds, 
a 9 x 4-inch set on edge requires 1G00 pounds, a 2 X C-inch, 3600 pounds, 
a 2 X 8-inch piece 6400 pounds to break it. If a piece 2 by 4 inches and 
10 feet long breaks with 1600 pounds, a 2 X 4-inch and 12 feet long piece 
breaks with about 1300 pounds, one 16 feet with 1000 pounds, etc.; and if 
a factor of safety of 10 is allowed, only one tenth of the above loads are 

permissible. 

A board i inch by 12 inches and 10 feet long contains as much wood 
as a 3 X 2-inch of the same length, and if placed edgewise should offer- 
four times as much resistance to breaking. Owing to its small bre-idth. 


238 


THE MATERIALS OF CONSTRUCTION. 


however, it “twists” when loaded, and in most cases, therefore, bears 
less than the 2 X 3-inch. To prevent this twisting, joists are braced, and 
the depth of timbers is made not to exceed four times their thickness. 

Short deep pieces shear out or split before their strength in bending can 
fully be called into play. 

To allow for normal irregularities in the structure of wood itself, as well 
as in the ao-sreffate structure of timbers, an allowance is made on the nuni- 
bers which have been found by experiment; this allowance is called the “ fac¬ 
tor of safety.” Where the selection of the wood is not very perfect, the load 
is a variable one, and the safety of human life depends on the structure, the 
factor is usually taken quite high, as much as G or 10; i.e., only one sixth or 
one tenth of the figures given in the tables is considered safe, and the beam 
is made six to ten times as heavy as the calculation requires. 

STRENGTH IN CROSS-BREAKING OF WELL-SEASONED SELECT PIECES. 


Common Names of Species. 

Strength of 
the Extreme 
Fibre 

Approximate Weight 
which breaks a Stick 

, 3 Wl 

J 2bh 2 

per Square 
Inch. 

1 by 1 Inch 
and 12 Inches 
Ipng. 

2 by 2 Inches 
and 10 Feet 
long. 


Pounds. 

Pounds. 

Pounds. 

(1) Robinia (locust), hard maple, hickory, oak, birch, 
best ash and elm, long-leaf, short-leaf, and 
Cuban pines, tamarack. 

13,000 

720 

570 

{2) Soft maple, cherry, ash, elm. walnut, inferior 
oak and birch, best poplar, Norway, loblolly, 
and pitch pines, black and white spruce, hem¬ 
lock and good cedar. 

10,000 

550 

440 

{3) Tulip, basswood, sycamore, butternut, poplars, 
white and other soft pines, firs, and cedars. .. 

6,500 

350 

280 


200. Tension and Compression.—When a piece of wood is pulled length¬ 
wise, in the manner shown in Fig. 108, part of the fibres are torn asunder 
or broken, but many are merely pulled or shredded out from between their 
neighbors. Since failure in tension thus involves lateral adhesion as well 
as strength of fibres, it is affected not only by the nature and dimensions 
of the fibres, but also by their arrangement. Owing to their transverse 
position the medullary rays (a large part of all woods) offer but one tenth 
to one twentieth as much resistance as the main body of fibres, and more¬ 
over weaken the timber by disturbing the straight course of the fibres and 
the regularity of the entire structure. 

The resistance is also much affected by the position of the grain. The 
perfectly cross-grained piece a (Fig. 109) sustains but about one tenth to 
one twentieth of the load which is supported by the straight-grained piece 
c, and it is evident that the piece b, which represents an excessive degree 
of cross-grain, is likewise weakened by the oblique position of the grain. 
















TIMBER. 


239 


This explains the detrimental influence of a knot on the under side of a 
board, as in Fig. 110. Since the lower side of the board, in bending, is, 
stretched, the upper side being compressed, the fibres of the lower side arc 
subjected to tension, and the wood of the knot, like the piece of cross-grained 


ffcAf 


f 


m 


'"Yl ■ 


i 


\7 


A 




i 1 ffii,, 


V 


Fig. 108. 

Specimen in Tension Test. 



Fig. 109.— Straight and Cross- 
grained Wood. 



Fig. 110.—Eifect of Knots and their 
Position. 


wood, offers but little resistance. Commonly the defect is greatly increased 
by a season-check in the knot itself, so that the knot affects the strength 
of the board like a saw-cut of equal depth, but to a less degree. 

Tested in compression endwise (Fig. Ill), the fibres act as so many 
hollow columns firmly grown together; and when the load becomes too 
great the piece fails in the manner illustrated in Fig. 113. 

This failure is a very complex phenomenon; in wood like 

pine the fibres of the plane in which failure occurs become jjjjljlj 

separated into small bodies; they tear apart and cease to 

behave as one solid body, but act as a large number of very 

small independent pieces. Like the strands of a rope these 

small bodies offer but little resistance to compression; they 

bend over, and the piece “ buckles.” 

It is evident that a vertical position and a regular ar- 
rangemejit of the fibres increase the resistance, and that -p I( , m _ Com- 
therefore the medullary rays and oblique position of fibres pression end. 
in cross-grained and knotty timber tend to reduce the wise, 
strength in compression. 

From the following table of strength in tension and compression it will 
be seen that these two are not always proportional, the stiffer conifers ex¬ 
celling in the latter, the tougher hard woods in the former. 



































































































































































































240 


TEE MATERIALS OF CONSTRUCTION. 


RATIO of strength in tension and compression, showing the dif- 


FERENCE BETWEEN RIGID CONIFERS AND TOUGH HARD WOODS. 

Name of Species. 

Ratio: 

tensile strength 

A Stick 1 Square Inch in Cross- 
section. 

Weight required to 

compressive strength 

Pull apart. 

Crush endwise. 

Hickory. 

3.7 

3.8 

2.3 

2.2 

Pounds. 

32,000 

29,000 

19,400 

17,300 

Pounds. 

8.500 

7.500 
8,600 
7,400 

Elm. 

Larch. 

Long-leaf pine. 



STRENGTH IN COMPRESSION OF COMMON AMERICAN WOODS IN WELL- 

SEASONED SELECT PIECES. 

(Approximate weight per square inch of cross-section requisite to crush a piece of wood endwise.) 

Pounds. 

{I) Black locust, yellow and cherry birch, hard maple, best hickory, long-leaf 


and Cuban pines, and tamarack. 9,000+ 

<2) Common hickory, oak, birch, soft maple, walnut, good elm, best ash, short- 

leaf and loblolly pines, Western hemlock, and Douglas fir. 7,000+ 

<3) Ash, sycamore, beech, inferior oak, Pacific white cedar, canoe cedar, Law- 
sou’s cypress, common red cedar, cypress, Norway and superior spruces, 

and fir. 6,000+ 

{4) Tulip, basswood, butternut, chestnut, good poplar, white and other common 

soft pines, hemlock spruce, and fir. 5,000+ 

(5) Soft poplar, white cedar, and some Western soft pines, and firs. 4,000+ 


201. Shearing.—When, in a structure like that shown in Fig. 112, a 
weight is placed on J and the tenon T by downward pressure breaks out 
the piece A BOD, this is said to shear out along the fibre. In the same 
manner, if the shoulder ABCD in Fig. 112 is pushed off along BD, it is 
sheared, and if BD and CE are each 1 inch, the surface thus sheared 


Fig. 112.—Longitudinal Shearing. 

off is 1 square inch, and the weight necessary to do this represents the 
shearing strength per square inch of the particular kind of wood. This 
resistance is small when compared to that of tension and compression. 
























































TIMBER. 


241 



Fig. 113 —Various Forms of Failure. A and B, compression endwise ; G , shearing (the 
bolt of a stirrup passed through the mortise and sheared out the end); D, tension. 
The lower figure indicates the number of pounds per square inch which produced 
the failure in tests by the Division of Forestry. No. 116 (upper figure on each 
piece) is white pine. Nos. 1, 2, and 5 are long-leaf pine, about one fifth natural size. 



























































242 


THE MATERIALS OF CONSTRUCTION. 


In general wet or green wood shears about one third more easily than 
dry wood; a surface parallel to the rings (tangent) shears more easily than 
one parallel to the medullary rays. The lighter conifers and hard woods 
offer less resistance than the heavier kinds, but the best of pine shears one 
third to one half more readily than oak or hickory, indicating that great 
shearing strengli is characteristic of <l tough ” woods. 

RESISTANCE TO SHEARING ALONG THE FIBRE. 

Pounds per 
Square Inch 


(1) Locust, oak, hickory, elm, maple, ash, birch. 1000 * 

(2) Sycamore, long-leaf, Cuban, and short-leaf pine, and tam¬ 

arack . 600 

(3) Tulip, basswood, better class of poplar, Norway, loblolly 

and white pine, spruce, red cedar. 400 

(4) Softer poplar, hemlock, white cedar, fir.. . 400 f 


Note. —Resistance to shearing, although a most important quality in wood, has not 
been satisfactorily studied. The values in the above table, taken from various authors, 
lack a reliable experimental basis and can be considered as only a little better than guess¬ 
work. See Results of Forestry Division Tests in Chapter XXXII. 

202. Influence of Weight and Moisture on Strength. —It has been stated 
that heavy wood is stronger than lighter wood of the same kind, and that 
seasoning increases all forms of resistance. Let us examine why this is so. 

Since the weight of dry wood depends on the number of fibres and the 
thickness of their walls, there must be more fibres per square inch of cross- 
section in the heavy than in the light piece of the same kind ,\ and it is but 
natural that the greater number of fibres should also offer greater resistance, 
i.e., have the greater strength. 

The beneficial influence of drying and consequent shrinking is twofold: 
(1) In dry wood a greater number of fibres occur per square inch, and (2) 
the wood-substance itself, i.e., the cell-walls, become firmer. A piece of 
green long-leaf pine, 1 by 1 inch and 2 inches long, is only about 0.94 by 
0.96 inch and 2 inches long when dry; its cross-section is 10 per cent 
smaller than before, but it still contains the same number of fibres. A 
dry piece 1 by 1 inch, therefore, contains 10 per cent more fibres than a 
green piece of the same size, and it is but fair to suppose that its resistance 
or strength is also about 10 per cent greater. 

The influence of the second factor, though unquestionably the more 
important one, is less readily measured. In 100 cubic inches of wood-sub¬ 
stance the material of the cell-walls takes up about 50 cubic inches of water 
and thereby swells up, becoming about 150 cubic inches in volume. In 
keeping with this swelling the substance becomes softer and less resistant. 

* Over. f Less tlmn. 

X This imperfect assumption is used only for comparison. 








TIMBER. 


243 


In pine wood this diminution of resistance, according to experiments) 
seems to be about 50 per cent, and the strength of the substance therefore 
is inversely as the degree of saturation or solution. 

203. Hardness.—Heavy wood is harder than lighter wood; the wood of 
the butt, therefore, is harder than that of the top, the darker summer wood 
harder than the light-colored spring wood. Moisture softens, and season¬ 
ing, therefore, hardens wood. Wood is much harder when pressed longi¬ 
tudinally than when pressed transversely to the fibres, and it is somewhat 
stronger tangentially than radially. Though harder wood resists saw and 
chisel more than softer wood, the working quality of the wood is not always 
a safe criterion of its hardness. 

The following indicates the hardness of our common woods:** 

1. Very hard woods requiring over 3200 pounds per square inch to pro¬ 
duce an indentation of one-twentieth inch: Hickory, hard maple, osage 
orange, black locust, persimmon, and the best of oak, elm, and hackberry. 

2. Hard woods requiring over 2400 pounds per square inch to produce 
an indentation of one-twentieth inch: Oak, elm, ash, cherry, birch, black 
walnut, beech, blue beech, mulberry, soft maple, holly, sour gum, honey- 
locust, coffee-tree, and sycamore. 

3. Moderately hard woods, requiring over 1600 pounds per square inch 
to produce an indentation of one-twentieth inch: The better qualities of 
Southern and Western hard pine, tamarack and Douglas spruce, sweet gum, 
and the lighter qualities of birch. 

4. Soft woods requiring less than 1600 pounds per square inch to pro¬ 
duce an indentation of one-twentieth inch : The greater mass of conifer¬ 
ous woods; pine, spruce, fir, hemlock, cedar, cypress, and redwood; poplar, 
tulip, basswood, butternut, chestnut, buckeye, and catalpa. 

204. Cleavability. —When an axe is struck into a piece of wood as shown 
in Fig. 114, the cleft projects beyond the bladeof the axe and the process is 

not one of cutting, but of tension across the grain. 
The axe presses on a lever, ab, while the surface in 
which the transverse tension takes place is reduced 
almost to a line across the stick at b. If the wood is 
very stiff, the cleft runs far ahead of the axe, the 
lever-arm ab is long, and the resistance to splitting 
proportionately small. A high modulus of elasticity, 
therefore, helps splitting, while great shearing strength, 
a good measure for transverse tension and hardness, 
hinder it. 

Wood splits naturally along two normal planes, the 
most readily along the radius, because the arrange- 
Fig. 114.—Cleavage, ment of fibres and pith-rays is radial, and next along 
the tangent, or with the annual rings, because the softer spring wood forms 
continuous planes in this direction. Cleavage along the radius, however, 

* The indentations here indicated are across the grain and in dry wood.—J. B. J. 

















































244 


THE MATERIALS OF CONSTRUCTION. 


is from 50 to 100 per cent easier, and only in case of cross-grain, etc., the 
cleavage along the ring becomes the easier. In the wood of conifers, wood- 
fibres and pith-rays are very regular, the former in perfect radial series or 
rows, and cleavage is, therefore, very easy in this direction. The same is 
brought about in the oak by the very wide pith-rays, but where they are 
thick and narrow, as in sycamore, and generally in the butt cuts and about 
knots, they impede cleavage by causing a greater irregularity in the course 
of the wood-fibres. The greater the contrast of spring and summer wood, 
the easier the cleavage tangentially or in the direction of the rings. This is 
especially marked in conifers and also in woods like oak, ash, and elm, where 
the spring wood appears as a continous series of large pores. Very slow 
growth influences tangential cleavage, narrow-ringed oak breaks out and 
splits less regularly even in a radial direction ; in conifers, however, this 
difference scarcely exists. Weight of wood affects the cleavage but little; in 
heavy wood the entrance of the axe, to be sure, is resisted with more force, 
but the greater rigidity of the wood, on the other hand, counterbalances this 
resistance. Irregularities in the course of the fibres, whether spiral growth, 
cross-grain, or inform of knots, all aid in resisting cleavage. Knotty sticks 
are split more easily from the upper end, since the cleft then runs around the 
knots (see Fig. 95). Moisture softens the wood and reduces lateral adhe¬ 
sion, and therefore wood splits more easily when green than when dry. 

205. Flexibility.* —Pine is brittle, hickory is flexible ; the former 
breaks, the latter bends. Being the opposite of stiffness, want of stiffness 
would seem to indicate flexibility. This, however, is only partly true; hick¬ 
ory and ash are stiff and yet among the most flexible of woods. Their 
small dimensions cause shavings and thin strands of most woods to appear 
pliable. For this reason the pliable, twisted wicker-willow is not a fair 
measure of the flexibility of the wood of this species. Generally hard 
woods are more flexible than conifers, wood of the butt surpassing in this 
respect that of the main part of the stem, the latter being usually superior 
to that of the limbs. Moisture softens wood and thereby increases its flexi¬ 
bility. Knots and cross-grain diminish flexibility, but the irregular struc¬ 
ture of elm, ash, etc. (particularly the arrangement of bodies of extremely 
firm fibres, like so many strands, among the softer tissue, as well as the 
interlacement of fibres due to post-cambial growth), favorably influences 
the flexibility of these woods. 

206. Toughness.f —So far the load by which the exhibition of the vari¬ 
ous kinds of strength in compression, tension, cross-bending, etc., was pro- 

* The writer here uses “ flexibility ” as Rankiue uses “ toughness,” that is, the ability 
to withstand great deformation before rupture. Flexibility, as the opposite of stiff¬ 
ness or rigidity, would signify the readiness to deflect under a given load, which is 
mathematically shown by a small modulus of elasticity.— J. 13. J. 

t The writer here uses toughness as indicating resilience, when this term is made to 
apply to the whole period of deformation and not simply to the elastic field.—J. B. J. 




TIMBER. 


245 


duced has always been assumed as applied slowly and gradually. When a 
wagon goes lumbering along a cobble pavement, the load on the spokes is 
not thus applied. Every stone deals the wheel a blow, and a mile’s 
journey means many thousand blows to every wheel-rim and spoke. In 
chopping, the axe-handle is jarred, and a handle made of pine wood, which 
shears easily along the fibre, would soon be shattered to pieces. Loads 
thus applied are “ shocks,” and resistance to this form of loading requires 
a combination of various kinds of strength possessed only by “ tough ” 
woods. Toughness is a familiar word to woodworkers, and yet is rarely 
defined. Tough wood must be both strong and pliable. Thus a willow is 
not tough when dry;' it is weak and brittle, and requires, notwithstanding 
its small lateral dimensions, to be moistened and twisted or sheared into 
still smaller strands so that its fibres are subjected almost exclusively to ten¬ 
sion if great deflection and great strength are to be combined (handles of 
wicker baskets). Hickory is both strong and pliable ; in the dimensions 
of a willow twig it can be used almost like a rope. The term “ tough,” 
therefore, is properly applied to woods like hickory and elm, and improp¬ 
erly to willow. 

Judging from the behavior of elm and hickory, wood may be pro¬ 
nounced “ tough ” if it offers great resistance to— 

(1) Longitudinal shearing over 1000 pounds per square inch, 

(2) Tension over 1G,000 pounds per square inch, 

and permits, when tested dry, of an aggregate combined distortion in 
compression and tension amounting to not less than 3 per cent. 

For instance, of a piece of dry hickory (//. alba) we may expect— 


Strength in shearing. pounds 1,200 

Strength in tension . do. 25,000 

Distortion in tension.per cent 2.03 

Distortion in compression. do. 1.55 

Total distortion. do. 3.58 


207. Practical Conclusions.—From the foregoing considerations a few 
valuable facts, mostly familiar to the thoughtful woodworker, may be 
deduced 

In framing, where light and stiff timber is wanted, the conifers excel; 
where heavy but steady loads are to be supported, the heavier conifers, hard 
pine, spruce, Douglas spruce, etc., answer as well as hard woods, which are 
costlier and heavier for the same amount of stiffness. On the other hand, 
if small dimensions must be used, and especially if moving loads are to be 
sustained, hard woods are safest, and in all cases where the load is applied 
in form of “ shocks” or jars, only the tougher hard woods should be em¬ 
ployed. The heavier wood surpasses the lighter of the same species in all 
kinds of strength, so that the weight of dry wood and the structural fea- 










246 


THE MATERIALS OF CONSTRUCTION\ 


tores indicative of weight may be used as safe signs in selecting timber for 
strength. 

In shaping wood it is better, though more wasteful, to split than to saw, 
because it insures straight grain and enables a more perfect seasoning. 

For sawed stock the method of "rift” or "quarter” sawing, which has 
so rapidly gained favor during the last decade, deserves every encourage¬ 
ment. It permits of better selection and of more advantageous disposition 
of the wood; rift-sawed lumber is stronger, wears better, seasons well, and 
is least subject to "working” or warping. 

All hardwood material which checks or warps badly during seasoning 
should be reduced to the smallest practicable size before drying, to avoid 
the injuries involved in this process; and wood once seasoned should never 
again be exposed to the weather, since all injuries due to seasoning are 
thereby aggravated. Seasoning increases the strength of wood in every 
respect, and it is therefore of great importance to protect w r ooden struc¬ 
tures bearing heavy weights against moisture. 

Knots , like cross-grain and other defects, reduce the strength of timber. 
Where choice exists, the knotty side of the joist should be placed upper¬ 
most, i.e., should be used in compression. 

Season-checks in timber are always a source of weakness; they are more 
injurious on the vertical than on the horizontal faces of a stringer or joist, 
and their effect continues even when they have closed up, as many do, and 
are no longer visible. 

Rafted timber , kiln-dried or steamed lumber are, as far as our present 
knowledge extends, as strong as other kinds; and wherever any of these pro¬ 
cesses aids in a more uniform or perfect seasoning, it increases the strength 
of the material. 

Pine " bled” for turpentine is as strong as "unbled.” 

Time of felling , whether season of the year or phase of the moon, does 
not influence strength, except that summer-felled hard wood rarely seasons 
as perfectly as that felled in the fall, and to this extent an indirect influence 
may be observed, as well as by the fact that fungi and insects have a better 
opportunity for developing. 

Warm countries and sunny exposures generally produce heavier and 
stronger timber, and conditions favorable to the growth of the species also 
improve its quality. But exceptions occur; neither fast nor slow growth is 
an infallible sign of strong wood, and it is the character of the annual ring, 
rather than its width, and particularly the proportion of summer wood, 
which determines the quality of the material. 

CHEMICAL PROPERTIES AND TECHNOLOGICAL PRODUCTS OF WOOD. 

208. Chemical Composition. —Wood dried at 300° F. is composed of over 
99 per cent of organic and less than 1 per cent of inorganic matter; the 
latter remains as ashes when wood is burned. 


TIMBER. 


247 


Wood consists of a skeleton of cellulose, permeare^ by a mixture 0 / 
other organic substances, collectively designated by the word lignin, and 
particles of mineral matter or ashes. 

Cellulose is the common substance of which plant-cells form their cases 
or walls; in flax, the entire fibre is almost pure cellulose, but the amount 
of cellulose obtained from wood, by the common processes, rarely exceeds 
one half of its dry weight. Cellulose is identical in composition with 
starch, but unlike the latter it resists alcoholic fermentation, though the 
plants themselves, as well as decay-producing fungi, are able to reconvert 
it into starch, from which it seems originally derived, and also to change it 
into various forms of sugar.* Lignin is as yet a chemical puzzle. The 
substances forming it are carbohydrates like cellulose itself, but of slightly 
different proportions and distinguished by greater solubility in acids, and 
by other chemical properties. 

In 100 pounds of wood (dried at 300° F.) and of cellulose the following 
proportions are found: 



Wood, 

Cellulose, 


Pounds. 

Pounds. 

Carbon. 

. 49 

44.4 

Hydrogen. 

. 6 

6.1 

Oxygen. 

. 44 

49.3 


This composition of wood is fairly uniform for different species. 

At ordinary temperatures wood is a very stable compound; both in air 
and under water it remains the same for centuries, and only when living 
organisms attack it with their strong solvents and convertants do change 
and decay set in. 

209. Wood as a Fuel.— Heated to 300° F. wood gives off only water, 
though some slight chemical changes are noticeable even at this tempera¬ 
ture. If the heat is increased, gases of pungent odor and taste are evolved; 
and if the temperature is sufficiently raised, the gases may be ignited, form¬ 
ing the flame of the fire, while the remaining solid part glows like an ignited 
charcoal, giving much heat, but no flame. The amount of heat produced 
by wood varies. If first dried at 300° F., 100 pounds of poplar wood should 
give as much heat as 100 pounds of hickory. In the natural state, however, 
this is not the case. 

The beneficial effect of thorough seasoning for firewood appears from 
the following consideration: 

One hundred pounds of wood as sold in the wood-yards contains in round 
numbers 25 pounds of water, 74 pounds of wood, and 1 pound of ashes. 

The 74 pounds of wood are composed of 37 pounds of carbon, 4.4 pounds 
of hydrogen, and 32 pounds of oxygen. 

* Chemists have succeeded in producing reconversion into grape-sugar; and though 
the methods thus far employed are expensive, it is to be expected that in the near future 
wood will become the principal source of both vinegar and alcohol. 







TEE MATERIALS OF CONSTRUCTION. 


24n 

In burning (which is a process of oxidation) 4 pounds of hydrogen aro 
already combined with 32 pounds of oxygen, and there are only the 37 pounds 
of carbon and 0.4 pound of hydrogen available in heat-production. Thus 
only about one half the weight of the wood-substance itself is heat-produc¬ 
ing, while every pound of water combined in the wood requires about 600 
units of heat to evaporate it, and thus diminishes the value of the wood as 
fuel. Hence under the most favorable circumstances 100 pounds of green 
wood (50 per cent moisture) furnishes about 270,000 units * of heat; 100 
pounds of half-dry (30 per cent moisture) about 410,000 units; 100 pounds 
of air-dry (20 per ce nt moisture) about 500,000 units; 100 pounds of air- 
dry (10 per cent moisture) about 580,000 units; 100 pounds of kiln-dry (2: 
per cent moisture) about 630,000 units. 

In the ordinary stove or other small apparatus the evil effect of moisture 
in the wood is very much increased, since combustion is materially interfered 
with. 

One hundred pounds of ordinary charcoal furnishes 1, 200,000 units of 
heat, but the same quantity of charcoal ]:>roduced at a temperature of 2000° 
F. furnishes 140,000 units of heat. 

Conifers and the lighter hard woods produce more flame, while the heavy 
hard woods furnish a good bed of live coal and exceed the former by 25 to 
30 per cent in production of heat with ordinary appliances. 

210. Charcoal. —Heated in a closed chamber or covered with earth, as in 
charcoal-pits, the wood is prevented from burning and a variety of changes 
occur, depending on the rate of heating. If the temperature is raised grad¬ 
ually so that the wood is heated several hours before a temperature of 600° 
F. is reached, the process is called dry distillation. In this process the wood 
is destroyed. It forms at first “ red ” or “ brown ” coal, still resembling 
wood, and finally charcoal proper. This coal is darker, heavier, conducts 
heat and electricity better, requires a greater heat to ignite, and produces 
more heat per pound in burning the higher the temperature under which it. 
is formed. 

One hundred pounds of wood (dried at 300° F.) leaves only about 30 
pounds of charcoal. In common practice much less charcoal (18 to 20 per 
cent) is produced. In this change from wood to coal the volume is dimin¬ 
ished by one half, so that a cord of wood which contains about 100 cubic 
feet of woo'd solid would be converted into 50 cubic feet at best. 

211. Products of Wood-distillation.— Of the 70 pounds of gaseous prod¬ 
ucts which 100 pounds of wood lose, during coaling, in being heated up to 
700° F., about 63 pounds become volatile before the temperature of 550° F. 
is reached. 

If condensed in a cooler, about three fourths of the 63 pounds of vol- 


* A uuit of heat in this case is the amount of heat which raises the temperature of 
1 pound of water 1° F. 





TIMBER. 


249 


sitile matter first evolved is found to be wood-vinegar, from which about 
4 pounds of pure acetic acid, the only source of perfectly pure vinegar, is 
obtained. Besides acetic acid, the liquid contains wood-spirits and a quan¬ 
tity of various allied substances. 

After the first stage of dry distillation, a large part of the products devel¬ 
oped cannot be liquefied in the ordinary cooler. They are gases like the 
illuminating-gas, mostly belonging to the marsh-gas series; they lack oxy¬ 
gen and thus show that the available oxygen has been nearly exhausted in 
the preceding part of the process. Products of the latter stages are tars 
and heavy oils, volatile only at high temperatures. Here also belong the 
substances,'known collectively as wood-creosote, employed as antiseptics in 
wood-impregnation. 

212. Cellulose. —Warmed in dilute nitric acid with a little chlorate of 
potash, the cells of a piece of wood may be separated. Each cell remains 
intact, but its wall is reduced in thickness and material; the lignin substances 
being dissolved out, only the cellulose is left. In commercial-cellulose 
manufacture, soda, sulphates, and of late chiefly sulphites are substituted 
for the nitric acid. The wood is chipped, boiled in the respective solution 
under high pressures, the residue is washed, and the remaining cellulose 
bleached and ready for use. As a matter of economy the residual liquid is 
evaporated and the soda used over again. 

213. Resin, Turpentine, and Lampblack. —When resinous wood, “fat 
pine,” “lightwood,” such as the knots and stumps of long-leaf, pitch, and 
other pines, is heated in a kiln or retort, the resins ooze out, are collected, 
and in distillation with steam yield turpentine and resin. The resins and 
their components vary with the species; the balsam of fir is limpid, its tur¬ 
pentine remains clear on exposure; the resin of pines is very viscid, their 
turpentines readily oxidize and darken when brought in contact with air. 
Resins are gathered more commonly either from cracks, such as “ wind ” and 
“ ring shakes,” as in the case of larch and fir (Venetian turpentine), or else 
from wounds made especially for this purpose, as in the case of naval stores 
gathered from pines. This latter process is known as “ bleeding,” “ tapping,” 
or “orcharding,” and is at present the principal method of obtaining tur¬ 
pentines and resins. 

On burning resinous wood, wood-tar, etc., in a smouldering fire, soot is 
deposited on the walls and partitions of the specially constructed soot-pit. 
It is then collected, but must be freed of various products of dry distilla¬ 
tion, by carefully heating to red heat, before it becomes the lampblack used 
in printer’s ink and otherwise much employed in the arts. 

214. Tannin. —Many kinds of wood and the bark of most trees contain 
tannin. To serve in tanning the bark must contain at least 3 per cent of 
tannin; the kind's mostly used vary from 5 to 15 per cent, and even the best 
probably never furnish over 20 per cent in the average. The use of tan- 
bark involves many disadvantages. It is difficult to dry and preserve, very 


2o0 


THE MATERIALS OF CONSTRUCTION. 


liable to mould, it is bulky and therefore expensive to ship and store, and 
very variable in the amount of tannin which it contains. 

To avoid these difficulties the tannic compounds are, in recent times, 
leached out of the finely ground bark and wood, condensed by evaporation, 
and shipped as extracts containing 20 to 40 per cent of tannin. 

The manufacture of pulp, and the production of fibre capable of being 
spun and woven, are also technological uses of wood which rely partly upon 
chemical reactions. 


DURABILITY AND DECAY OF WOOD. 

215. All Decay Produced by a Fungus-growth.—All wood is equally 

durable under certain conditions. Kept dry or submerged, it lasts indefi¬ 
nitely. Pieces of pine have been unearthed in Illinois which have lain 
buried GO or more feet deep for many centuries. Deposits of sound logs of 
oak, buried for unknown ages, have been unearthed in Bavaria; parts of the 
piles of the lake-dwellers, driven more than two thousand years ago, are 
still intact. 

On the radial section of a piece of pine timber, with one of the shelf-like 
fungus-growths, as shown in Fig. 115, both bark and wood are seen to be 
affected. A small particle of the half-decayed wood presents pictures like 
that of Fig. 116. Slender, branching threads are seen to attach themselves 
closely to the walls of the cells, and to pierce these in all directions. Thus 
these little threads of fungus mycelium soon form a perfect network in the 
wood, and as they increase in number they dissolve the walls, and convert, 
the wood-substance and cell-contents into sugar-like food for their own con¬ 
sumption. In some cases it is the woody cell-wall alone that is attacked. 
In other cases they confine themselves to eating up the starch found in the 
cells, as shown in Fig. 117, and merely leave a stain (bluing of lumber). In 
all cases of decay we find the vegetative bodies, these slender threads of 
fungi, responsible for the mischief. These fine threads are the vegetative 
body of the fungus; the little shelf is its fruiting-body, on which it pro¬ 
duces myriads of little spores (the seeds of fungi). Some fungi attack onlv 
conifers, others hard woods ; many are confined to one species of tree, and 
perhaps no one attacks all kinds of wood. One kind produces “ red rot,” 
others “ bluing.” In one case the decayed tracts are tabular, and in the 
direction of the fibres the wood is “ peggy.” In other cases no particular 
shapes are discernible. 

Cutting off a disk of loblolly pine, washing it, and then laying it in a 
clean, shady place in the sawmill, its sap wood will be foumd stained in a 
few days. Nor is this mischief confined to the surface; it penetrates the 
sapwood of the entire disk. From this it appears that the spores must have 
been in the air about the mill, and also that their germination and the 
growth of the threads or mycelium are exceedingly rapid. (Watching the 


TIMBER. 


251 


progress of mould on a piece of bread teaches the same thing.) Placing a 
fresh piece of sapwood on ice, another into a dry kiln, and soaking a few 
others in solutions of corrosive sublimate (mercuric chloride) and other sim¬ 
ilar salts, we learn that the fungus-growth is retarded by cold, prevented 
and killed by temperatures over 150° F., and that salts of mercury, etc., 
have the same effect. The fact that seasoned pieces if exposed are not so 




Fig. 115.— “Shelf” Fungus on the Stem of a Pine. (Hartig.) «, sound wood; b, 
resinous “light” wood; c, partly decayed wood or punk; d, layer of living spore- 
tubes; 6, old filled-up spore-tubes; /, fluted upper surface of the fruiting-body of 
the fungus, which gets its food through a great number of fine threads (the my¬ 
celium). its vegetative tissue penetrating the wood and causing its decay. 

Fig. no.—Fungus-threads in Pine Wood. (Hartig.) a, cell-wall of the wood fibres ; 
b, bordered pits of these fibres; c, thread of mycelium of the fungus; d, holes in 
the cell-walls made by the fungus-threads, which gradually dissolve the walls as 
shown at e, and thus break down the wood-structure. 

readily attacked by fungi shows that the moisture in air-dried wood is insuf¬ 
ficient for fungus growth. 

From this it appears that warmth, preferably between 60° and 100° F., 
combined with abundance of moisture (but not immersion), is the most 
important condition favoring decay, and that the defence lies in the proper 
regulation or avoidance of these conditions, or else in the use of poisonous 
salts, which prevent the propagation of fungi. 






























































252 


THE MATERIALS OF CONSTRUCTION. 


It is also apparent, therefore, why w T ood decays faster in Alabama than 
in Wisconsin, faster in the swamps than on the plains, and why the presence 
of large quantities of decaying wood about the yard, constantly producing 
fresh supplies of spores, stimulates decay. Covering with tar or impregnat¬ 
ing with creosote, salts of mercury, cop¬ 
per, etc., enables even sap wood to last 
under the most trying conditions. Con¬ 
tact with the ground assures most favor¬ 
able moisture conditions for fungus- 
-S growth, and the higher temperatures 
near the surface of the ground, together 
with the ever-present supply of spores, 
cause rot in a post to start at the sur¬ 
face more readily than 30 inches below. 

216. Prevention of Decay.—The 
use of means to jwevent decay is there¬ 
fore desirable where timber is placed in 
positions favorable to fungus-growth, 
as in railway ties; and all joists and tim¬ 
ber in contact with damp brick walls, as 
also all building material whose perfect 
seasoning is prevented by the absence 
of proper circulation of air, should be 
specially protected. In the former cases 
it is economy to apply preservative proc¬ 
esses; in the latter a sanitary necessity. 
Wood covered with paint, etc., before 
it is perfectly seasoned falls a prey to 
“dry-rot ” ; the fungus finds abundance 
of moisture, and the protection intended 
Fig. 117.— Cells of Maple-wood attacked for the wood protects its enemy, the 
by Fungus-threads ( Nectria cinna- fungus. Since charcoal resists the sol- 

barina Mayer). Section of three vents of fungi, charring the outer parts 
wood-fibres showing the threads of the 



of posts makes, if well done, namely, so 
as not to open checks into the interior 
of the wood, a very fine protection. 

Under ordinary circumstances, only 
Stroyed starch-grains; d, dead por- the second great factor of decay, i.e., 
tions of the fungus-thread together tlle mo i stu re condition, can be con- 


fungus branching in their cavities and 
consuming the starch stored in these 
cells, a, interior or cavity of cells ; b, 
threads of the fungus ; c, partly de- 


with debris ; e, holes bored 
fungus through the cell-walls 
starch grains just being attacked. 


U “ e trolled. 

by 


Perfect seasoning, preferably kiln- 
drying, before using, and protection 
against the entrance of moisture by tar, paints, and other covers, when put 
in place, prolong the life of wooden structures. Where such a covering is 
too expensive, good ventilation at least is necessary. Contact-surfaces, 









































































TIMBER. 


253 


where timber rests on timber or brick, should in all cases be especially pro¬ 
tected. 

Different species differ in their resistance to decay. Cedar is more 
durable than pine, and oak better than beech; but in most cases the condi¬ 
tions of warmth and moisture in particular locations have so much to do 
with durability that often an oak post outlasts one of cedar, even in the same 
line of fence, and predictions of durability become mere guesswork. 

Containing more ready-made food, and in forms acceptable to a great 
number of different kinds of fungi, the sapwood is more subject to decay 
than the heartwood, doubly so where the latter is protected by resinous sub¬ 
stances, as in pine and cedar. Several months of immersion improves the 
durability of sapwood, but only impregnation with preservative salts seems 
to render it perfectly secure. Once attacked by fungi, wood becomes pre¬ 
disposed to further decay. 

Wood cut in the fall is more durable than that cut in summer,* only 
because the low temperature of the winter season prevents the attack of the 
fungi, and the wood is thus given a fair chance to dry. Usually summer- 
felled wood, on account of prevalent high temperature and exposure to sun, 
checks more than winter-felled wood; and since all season-checks favor the 
entrance of both moisture and fungus, they facilitate destruction. Where 
summer-felled wood is worked up at once and protected by kiln-drying, no 
difference exists. (The phases of the moon have no influence whatever on 
durability!) 

In sawing timber much of the wood is bastard-cut; at these places water 
enters much more readily, and for this reason split and hewn timber and 
ties generally resist decay perhaps better than if sawed. 

The attacks of beetles, us well as those of the shipworm, cannot here be 
considered; like chisel or saw they are mechanical injuries against which 
none of our woods are proof, except by impregnation of creosote or other 
chemical. 

RANGE OF DURABILITY IN RAILROAD-TIES. 


Years. 


White oak and chestnut oak. 8 

Chestnut.... 8 

Black locust. 10 

Cherry, black walnut, locust.. 7 

Elm.. 6 to 7 

Red and black oaks.4 to 5 

Ash, beech, maple. 4 


Years. 


Redwood. 12 

Cypress and red cedar.... 10 

Tamarack.7 to 8 

Long-leaf pine. 0 

Hemlock...4 to 6 

Spruce. 5 


The durability of wood exposed to the changes of the weather and 
where painting, after thorough seasoning, is impracticable, is increased by 
impregnating it with various salts or other chemicals which prevent the 
fungus from feeding on the wood. The wood is first steamed, to open the 
pores and remove the hardened surface coating of sap and dirt, and a liquid 
solution of the preservative material is then injected with the assistance of 


Iieat and pressure.__ 

* Timber is most durable when cut at the time it contains the least sap. Ibis time 
varies with the locality and with the climatic conditions.—J. B. J. 




















254 


TEE MATERIALS OF CONSTRUCTION. 


The most efficient fluids used on a large scale are bichloride of zinc and 
creosote, or both combined. The “ life ” of railroad-ties is thereby increased 
to twice and three times its natural duration. 

HOW TO DISTINGUISH THE DIFFERENT KINDS OF WOOD.* 

217. An Examination of the Structure Essential to Identification. —The 

carpenter or other artisan who handles different woods becomes familiar with 
those he employs frequently, and learns to distinguish them through this 
familiarity, without usually being able to state the characteristic differences. 

If a wood comes before him with which he is not familiar, he has, of course, 
no means of determining what it is, and it is possible to select pieces even of 
those with which he is well acquainted, different in appearance from the 
average, that will make him doubtful as to their identification. Further¬ 
more, he may distinguish between hard and soft pines, between oak and 
ash, or between maple and birch, which are characteristically di fferent; but 
when it comes to distinguishing between the several species of pine or oak 
or ash or birch, the absence of readily recognizable characteristics is such 
that but few practitioners can be relied upon to do it. Hence in the 
markets we find many species mixed and sold indiscriminately. 

To identify the different woods it is necessary to have a knowledge of 
the definite, invariable differences in their structure, besides that of the 
often variable differences in their appearance. These structural differences 
may either be readily visible to the naked eye or with a magnifier, or they 
may require a microsocpical examination. In some cases such an examina¬ 
tion cannot be dispensed with if we would make absolutely sure. There are 
instances, as in the pines, where even our knowledge of the minute anatom¬ 
ical structure is not yet sufficient to make a sure identification. 

218. A Structural Key to Species. —In the following key an attempt has 
been made—the first, so far as we know, in English literature—to give a 
synoptical view of the distinctive features of the commoner "woods of the 
Fnited States which are found in the markets or are used in the arts. It 
will be observed that the distinction has been carried in most instances no 
further than to genera or classes of w T oods, since the distinction of species 
can hardly be accomplished without elaborate microscopic study, and also 
that, as far as possible, reliance has been placed only on such characteristics 
as can be distinguished with the naked eye or a simple magnifying-glass, in 
order to make the key useful to the largest number. Recourse has also^ 
been taken for the same reason to the less reliable and more variable general 
external appearance, color, taste, smell, weight, etc. 

The user of the key must, however, realize that external appearance, 
such, for example, as color, is not only very variable, but also very difficult 
to describe, individual observers differing especially in seeing and describing 

* The matter in the remainder of this chapter is mostly the joint product of Dr. ' 
B. E. Fernow and Mr. Filibert Roth. 



TIMBER. 


255- 


shades of color. The same is true of statements of size when relative and 
not accurately measured, while weight and hardness can perhaps be more 
readily approximated. Whether any feature is distinctly or only indistinctly 
seen will also depend somewhat on individual eyesight, opinion, or practice. 
In some cases the resemblance of different species is so close that only one 
other expedient will make distinction possible, namely, a knowledge of the 
region from which the wood has come. We know, for instance, that no 
long-leaf pine grows in Missouri or Arkansas, and that no white pine can 
come from Alabama, and we can separate the white cedar, giant arbor vitas 
of the West and the arbor vitas of the Northeast only by the difference of 
the locality from which the specimen comes. With all these limitations 
properly appreciated, the key will be found helpful toward greater familiar¬ 
ity with the woods which are more commonly met with. 

219. Characteristic Structural Features.—The features which have been 
utilized in the key and with which (their names as well as their appearance), 
therefore, the reader must familiarize himself before attempting to use 
the key, are mostly described as they appear in cross-section. They are: 

(1) Sapwood and heartwood (see Art. 180), the former being the wood 
from the outer, and the latter from the inner, part of the tree. In some-. 



Fig. 118.—“Non-porous” Woods. A, fir; B, “hard” pine; G, soft pine, ar, annual 
ring; o. e., outer edge of ring; i. e., inner edge of ring; s. w., summer wood; sp. id., 
spring wood; rd, resin-ducts. 

cases they differ only in shade, and in others in kind of color, the heartwood 
exhibiting either a darker shade or a pronounced color. Since one cannot 
always have the two together, or be certain whether he has sapwood or 
heartwood, reliance upon this feature is, to be sure, unsatisfactory, yet 
sometimes it is the only general characteristic that can be relied upon. If 
further assurance is desired, microscopic structure must be examined; in 
such cases reference has been made to the presence or absence of tracheids in 
pith-rays and the structure of their walls, especially projections and spirals. 

(2) Annual rings, their formation having been described in Art. 181. 
(See also Figs. 118, 120.) They are more or less distinctly marked, and by 
means of such marking a classification of three great groups of wood is. 

possible. 

(3) Spring wood and Summer wood , the former being the interior (first- 
formed wood of the year), the latter the exterior (last-formed) part of the 
























256 


THE MATERIALS OF CONSTRUCTION. 


ring. The proportion of each and the manner in which the one merges into 
the other are sometimes used, but more frequently the manner in which the 
pores appear distributed in either. 



Fig. 119.—“ Ring-porous ” Woods—White Oak and hickory, a. r., annual ring; su. w., 
summer wood; sp. w., spring wood; v, vessels or pores; c. L, “ concentric” lines; rt, 
darker tracts of hard fibres forming the firm part of oak wood; pr, pith-rays. 

(4) Pores , which are vessels cut through, appearing as holes in cross- 
section, in longitudinal section as channels, scratches, or indentations. (See 
p. 213 and Figs. 119 and 120.) They appear only in the broad-leaved, 
so-called, hard woods; their relative size (large, medium, small, minute, and 
indistinct, when they cease to be visible individually by the naked eye) and 
manner of distribution in the ring being of much importance, and especially 
in the summer wood, where they appear singly, in groups, or short broken 
lines, in continuous concentric, often wavy, lines, or in radial branching 
lines. 

(5) Resin-ducts (see p. 210 and Fig. 118), which appear very much like 
pores in cross-section, namely, as holes or lighter or darker colored dots, but 
much more scattered. They occur only in coniferous woods, and their 
presence or absence, size, number, and distribution are an important dis¬ 
tinction in these woods. 



Fig. 120. —“ Diffuse porous” Woods, ar, annual ring; pr, pith rays which are “broad” 

at a, “fine ” at b, “ indistinct” at d. 

(6) Pitli-rays (see Art. 184 and Figs. 119 and 120), which in cross- 
section appear as radial lines, and in radial section as interrupted bands of 
varying breadth, impart a peculiar lustre to that section in some woods. 





































































































































































































TIMBER. 


25? 


They are most readily visible with the naked eye or with a magnifier in the 
broad-leaved woods. In coniferous woods they are usually so fine and 
closely packed that to the casual observer they do not appear. Their breadth 
and their greater or less distinctness are used as distinguishing marks, being 
styled fine, broad, distinct, very distinct, conspicuous, and indistinct when 
no longer visible by the naked (strong) eye. 

(7) Concentric lines , appearing in the summer wood of certain species 
more or less distinct, resembling distantly the lines of pores, but much finer 
and not consisting of pores. (See Fig. 119.) 

Of microscopic features, the following only have been referred to: 

(8) Tracheids , a description of which is to be found in Art. 185. 

(9) Pits , simple and bordered, especially the number of simple pits in 
the cells of the pith-rays, which lead into each of the adjoining tracheids. 

For standards of weight, consult table in Art. 191; for standards of 
hardness, the classification in Art. 203. 

Unless otherwise stated the color refers always to the fresh cross-section 
of a piece of dry wood; sometimes distinct kinds of color, sometimes only 
shades, and often only general color effects appear. 

220. The Use of the Key. —Nobody need expect to be able to use success' 
fully any key for the distinction of woods or of any other class of natural 
objects without some practice. This is especially true with regard to woods, 
which are apt to vary much, and when the key is based on such meagre 
general data as the present. The best course to adopt is to supply one’s self 
with a small sample collection of woods accurately named.* Small, polished 
tablets are of little use for this purpose. The pieces should be large enough, 
if possible, to include pith and bark, and of sufficient width to permit ready 
inspection of the cross-section. By examining these with the aid of the 
key, beginning with the better-known woods, one will soon learn to see the 
features described and to form an idea of the relative standards which the 
maker of the key had in mind. To aid in this, the accompanying illustra¬ 
tions will be of advantage. When the reader becomes familiar with the key, 
the work of identifying any given piece will be comparatively easy. The 
material to be examined must, of course, be suitably prepared. It should be 
moistened; all cuts should be made with a very sharp knife or razor and be 
clean and smooth, for a bruised surface reveals but little structure. The 
most useful cut may be made along one of the edges. Instructive, thin, 
small sections may be made with a sharp penknife or razor, and when placed 
on a piece of thin glass, moistened and covered with another piece of glass, 
they may be examined by holding them toward the light. 

Finding, on examination with the magnifier, that it contains pores, we 
know it is not coniferous or nonporous. Finding no pores collected in the 
spring-wood portion of the annual ring, but all scattered (diffused) through 

* Hough’s Wood Sections will be found both helpful and pleasing. About one hun¬ 
dred and fifty species of American woods are now so prepared by Mr. Itomeyn Hough, 
Lowville, N. Y.—J. B. J. 






258 


THE MATERIALS OF CONSTRUCTION. 


the ring, we turn at once to the class of “ dilfuse-porous woods.” We now 
note the size and manner in which the pores are distributed through tha 
ring. Finding them very small and neither conspicuously grouped, nor 
larger nor more abundant in the spring wood, we turn to the third group of 
this class. We now note the pith-rays, and finding them neither broad nor 
conspicuous, but difficult to distinguish even with the magnifier, we at 
once exclude the wood from the first two sections of this group and place it 
in the third, which is represented by only one kind, cottonwood. Finding 
the wood very soft, white, and on the longitudinal section with a silky lustre, 
we are further assured that our determination is correct. We may now turn 
to the list of woods and obtain further information regarding the occurrence, 
qualities, and uses of the wood. 

Sometimes our progress is not so easy; we may waver in what group or 
section to place the wood before us. In such cases we may try each of the 
doubtful roads until we reach a point where we find ourselves entirely wrong 
and then return and take up another line; or we may anticipate some of the 
later-mentioned features and, finding them apply to our specimen, gain 
additional assurance of the direction we ought to travel. Color will often 
help us to arrive at a speedy decision. In many cases, especially with con¬ 
ifers, which are rather difficult to distinguish, a knowledge of the locality 
from which the specimen comes is at once decisive. Thus, Northern white 
cedar, and bald cypress, and the cedar of the Pacific will be identified even 
without the somewhat indefinite criteria given in the key. 

Engineers and architects can, in the case of the two leading kinds of 
Southern pine (long-leaf, P. palustris , and short-leaf, P. ecliinata), usually 
determine the species by learning with certainty where the lumber was 
sawed. This is the more easy with large orders as these are filled directly 
from the mills, and the shipping bills for the particular cars on which it is 
delivered may be demanded. The two maps shown in Plates V and VI * 
will serve to identify the species when the locality is known. It will be 
seen at once that these two species do not often occupy the same territory. 

221. Key to the More important Woods of North America. 

[The numbers preceding names refer to the List of "Woods following the Key.] 

I. Non-porous Woods.—Pores not visible or conspicuous on cross-section even 
With magnifier. Annual rings distinct by denser (dark-colored) bands of summer 
wood (Fig. 118). 

II. Ring-porous Woods.—Pores numerous, usually visible on cross-section with¬ 
out, magnifier. Annual rings distinct by a zone of large pores collected in the spring 
wood, alternating with the denser summer wood (Fig. 119). 

III. Diffuse-porous Woods.—Pores numerous, usually not plainly visible on 
cross-section without magnifier. Annual rings distinct by a fine line of denser 
summer-wood cells, often quite indistinct; pores scattered through annual ring, no 
zone of collected pores in spring wood (Fig. 120). 

* These maps are reduced from similar ones published by the Forestry Division of 
the U. S. Agr. Dept. Washington, as Bulletin No. 13. See plates opposite p. 684. 







TIMBER. 


259 


Note.—T he above-described three groups are exogenous, i.e., they grow by add¬ 
ing annually wood on their circumference. A fourth group is formed by the endog¬ 
enous woods, like yuccas and palms, which do not grow by such additions. 

I. NON-POROUS WOODS. 

Includes all coniferous woods. 

A. Resin-ducts wanting.* 

1. No distinct heartwood. 

a. Color effect yellowish white ; summer wood darker yellowish (under 

microscope pith-ray without tracheids).(Nos. 9-13) Firs. 

b. Color effect reddish (roseate) (under microscope pith-ray with tra¬ 

cheids) .(Nos. 14 and 15) Hemlock. 

2. Heartwood present, color decidedly different in kind from sapwood. 

a. Heartwood light orange-red ; sapwood pale lemon ; wood heavy and 

hard.(Ho. 38) Yew. 

b Heartwood purplish to brownish red ; sapwood yellowish white ; wood 
soft to medium hard light, usually with aromatic odor. 

(No. 6) Red Cedar. 

c. Heartw r ood maroon to terra cotta or deep brownish red ; sapwood light 

orange to dark amber, very soft and light, no odor ; pith-rays very 
distinct, specially pronounced on radial section .. .(No. 7) Redwood. 

3. Heartwood present, color only different in shade from sapw r ood, dingy- 

yellowish brown. 

a. Odorless and tasteless.(No. 8) Bald Cypress. 

b. Wood with mild resinous odor, but tasteless. .(Nos. 1-4) White Cedar. 

c. Wood with strong resinous odor and peppery taste when freshly cut. 

(No. 5) Incense-cedar. 


ADDITIONAL NOTES FOR DISTINCTIONS IN THE GROUP. 

Spruce is hardly distinguishable from fir, except by the existence of the resin- 
ducts, and microscopically by the presence of tracheids in the medullary rays. 
Spruce may also be confounded with soft pine, except for the heartwood color of the 
latter and the larger, more frequent, and more readily visible resin-ducts. 

In the lumber-yard hemlock is usually recognized by color and the slivery char¬ 
acter of its surface. Western hemlocks partake of this last character to a less 
degree. 

Microscopically the white pine can be distinguished by having usually only one 
large pit, while spruce shows three to five very small pits in the parenchyma-cells of 
the pith-ray communicating with the tracheid. 

The distinction of the pines is possible only by microscopic examination. The 
following distinctive features may assist in recognizing, when in the log or lumber- 
pile, those usually found in the market : 

The light, straw color, combined with great lightness and softness, distinguishes 
the white pines (white pine and sugar-pine) from the hard pines (all others in the 
market), which may also be recognized by the gradual change of spring wood into 
summer wood. This change in hard pines is abrupt, making the summer wood 
appear as a sharply defined and more or less broad band. 

The Norway pine, which may be confounded with the short-leaf pine, can be dis- 

* To discover the resin-ducts a very smooth surface is necessary, since resin-ducts are frequently 
seen only with difficulty, appearing on the cross-section as fine whiter or darker spots normally scat¬ 
tered singly, rarely in groups, usually in the summer wood of the annual ring. They are often much 
more easily seen on radial, and still more so on tangential, sections, appearing there as fine lines or 
dots of open structure of different color, or as indentations or pin-scratches in a longitudinal direction. 










260 


THE MATERIALS OF CONSTRUCTION. 


B. Resin-ducts present. 

1. No distinct heartwood ; color white, resin-ducts very small, not numerous. 

(Nos. 33-36) Spruce. 


2. Distinct heartwood present. 

a. Resin-ducts numerous, evenly scattered through the ring. 

a'. Transition from spring wood to summer wood gradual: annual 
ring distinguished by a fine line of dense summer-wood cells ; 
color white to yellowish red ; wood soft and light. 

(Nos. 18-21) Soft Pines.* 
b’. Transition from spring wood to summer wood more or less 
abrupt; broad bands of dark-colored summer wood ; color 
from light to deep orange ; wood medium hard and heavy. 

(Nos. 22-32) Hard Pines.* 

b. Resin-ducts not numerous nor evenly distributed. 

a'. Color of heartwood orange-reddish, sapwood yellowish (same as 
hard pine); resin-ducts frequently combined in groups of 8 to 
30, forming lines on the cross-section (tracheids with spirals). 

(No. 37) Douglas Spruce. 
b'. Color of heartwood light russett-brown ; of sapwood yellowish 
brown ; resin-ducts very few, irregularly scattered (tracheids 
without spirals).(Nos. 16 and 17) Tamarack. 


II. KING-POROUS WOODS. 

[Some of Group D and cedar-elm imperfectly ring-porous. J 

A. Pores in the summer wood minute, scattered singly or in groups, or in short 
broken lines, the course of which is never radial. 


tinguished by being much lighter and softer. It may also, but more rarely, be 
confounded with heavier white pine, but for the sharper definition of the annual 
ring, weight, and hardness. 

The long-leaf pine is strikingly heavy, hard, and resinous, and usually very reg¬ 
ular and narrow-ringed, showing little sapwood, and differing in this respect from 
the short-leaf pine and loblolly pine, which usually have wider rings and more sap- 
wood, the latter excelling in that respect. 

The following convenient and useful classification of pines into four groups, 
proposed by Dr. H. Mayr, is based on the appearance of the pith-ray as seen in a 
radial section of the spring wood of any ring : 

Section I. Walls of the tracheids of the pith-ray with dentate projections. 

a. One to two large, simple pits to each tracheid on the radial walls of the 

cells of the pith-ray.—Group 1. Represented in this country only by P. 
resinosa. 

b. Three to six simple pits to each tracheid, on the walls of the cells of the 

pith ray.—Group 2. P. tceda, palustris, etc., including most of our 
“hard” and “ yellow” pines. 

Section II. Walls of tracheids of pith-ray smooth, without dentate projections. 

a. One or two large pits to each tracheid on the radial walls of each cell of 

the pith-ray.—Group 3. P. strobus , lambertiana , and other true white 
pines. 

b. Three to six small pits on the radial walls of each cell of the pith-ray. 

Group 4. P. parry ana and other nut-pines, including also P. bal- 
fouriana. 


* Soft and hard pines are arbitrary distinctions, and the two are not distinguishable at the common 
limit. 







TIMBER . 


261 


1. Pith-rays minute, scarcely distinct. 

a. Mood heavy and hard; pores in the summer wood not in clusters. 

a'. Color of radial section not yellow.(Nos. 39-44) Ash. 

l>. Color of radial section light yellow; by which, together with its 
hardness and weight, this species is easily recognized. 

(No. 103) Osage Orange. 

b. Wood light and soft; pores in the summer wood in clusters of 10 to 30. 

(No. 56) Catalpa. 

2. Pith-rays very fine, yet distinct; pores in summer wood usually single or 

in short lines; color of heartwood reddish brown; of sapwood yellowish 
white; peculiar odor on fresh section.(No. Ill) Sassafras. 

3. Pith-rays fine, but distinct. 

a. Very heavy and hard; heartwood yellowish brown. 

(No. 77) Black Locust. 

b. Heavy; medium hard to hard. 

a'. Pores in summer wood very minute, usually in small clusters of 
3 to 8; heartwood light orange-brown. 

(No. 83) Red Mulberry. 
b\ Pores in summer wood small to minute, usually isolated; heart- 
wood cherry-red.(No. 61) Coffee-tree. 

4. Pith-rays fine, but very conspicuous, even without magnifier. Color of 

heartwood red; of sapwood pale lemon.(No. 78) Honey-locust. 

ADDITIONAL NOTES FOR DISTINCTIONS IN THE GROUP. 

Sassafras and mulberry may be confounded but for the greater weight and hard¬ 
ness and the absence of odor in the mulberry; the radial section of mulberry also 
shows the pith-rays conspicuously. 

Honey-locust, coffee-tree, and black-locust are also very similar in appearance. 
The honey-locust stands out by the conspicuousness of the pith-rays, especially on 
radial sections, on account of their height, while the black locust is distinguished by 
the extremely great weight and hardness, together with its darker brown color. 



The ashes, elms, hickories, and oaks may, on casual observation, appear to 
resemble one another on account of the pronounced zone of porous spring wood. 
The sharply defined large pith-rays of the oak exclude these at once; the wavy lines 
of pores in the summer wood, appearing as conspicuous finely-feathered hatchings 
on tangential section, distinguish the elms; while the ashes differ from the hickory 
by the very conspicuously defined zone of spring-wood pores, which in hickory 
appear more or less interrupted. The reddish hue of the hickory and the more or 
less brown hue of the ash may also aid in ready recognition. The smooth, radial 
surface of split hickory will readily separate it from the rest. 













































262 


TUE MATERIALS OF CONSTRUCTION. 


B. Pores of summer wood minute or small, in concentric wavy and sometimes 

branching lines, appearing as finely-feathered hatchings on tangential 
section. 

1. Pith-rays fine, but very distinct; color greenish white. Heart wood absent 

or imperfectly developed.(No. 70) Hackberry. 

2. Pith-rays indistinct; color of heartwood reddish brown; sap wood grayish 

to reddish white. } ..(Nos. 62-66) Elms. 

C. Pores of summer wood arranged in radial branching lines (when very crowded 

radial arrangement somewhat obscured). 

1. Pith-rays very minute, hardly visible .(Nos. 58-60) Chestnut. 

2. Pith-rays very broad and conspicuous.(Nos. 84-102) Oak. 

D. Pores of summer wood mostly but little smaller than those of the spring wood, 

isolated and scattered; very heavy and hard woods. The pores of the 
spring wood sometimes form but an imperfect zone. (Some diffuse-porous 
woods of groups A and B may seem to belong here.) 

1. Fine concentric lines (not of pores) as distinct, or nearly so, as the very fine 

pith-rays; outer summer wood with a tinge of red; heartwood light reddish 
brown.(Nos. 71-75) Hickory. 

2. Fine concentric lines, much finer than the pith-rays; no reddish tinge in 

summer wood; sapwood white; heartwood blackish..(No. 105) Persimmon. 


ADDITIONAL NOTES FOR DISTINCTIONS IN THE GROUP. 



Fig, 122.—A, Black Ash; B, White Ash; C, Green Ash. 


The different species of ash may be identified as follows: 

1. Pores in the summer wood more or less united into lines. 

a. The lines short and broken, occurring mostly near the limit of the ring. 

(No. 39) White Ash. 

b. The lines quite long and conspicuous in most parts of the summer 

wood.(No. 43) Green Ash. 

2. Pores in the summer wood not united into lines, or rarely so. 

a. Heartwood reddish brown and very firm.(No. 40) Red Ash. 

b. Heartwood grayish brown and much more porous. .(No. 41) Black Ash! 









































































































































































TIMBER. 


263 


additional notes— continued. 

In the oaks two groups can be readily distinguished by the manner in which the 
pores are distributed in the summer wood. In the white oaks the pores are very fine 
and numerous and crowded in the outer part of the summer wood, while in the black 
or red oaks the pores are larger, few in number, and mostly isolated. The live oaks, 
as far as structure is concerned, belong to the black oaks, but are much less porous, 
and are exceedingly heavy and hard. 



Fig. 123 —Wood of Red Oak. (For White Oak see Fig. 119.) 










































































































































































































































264 


TEE MATERIALS OF CONSTRUCTION. 


III. DIFFUSE-POROUS WOODS. 

[A few indistinctly ring-porous wooa i of Group II, D, and cedar-elm may seem to belong here.] 

A. Pores varying in size from large to minute; largest in spring wood, thereby giving 

sometimes the appearance of a ring-porous arrangement. 

1. Heavy and hard; color of heartwood (especially on longitudinal section) 

chocolate-brown,.(No. 116) Black Walnut. 

2. Light and soft; color of heartwood light reddish brown..(No. 55) Butternut. 

B. Pores all minute and indistinct; most numerous in spring wood, giving rise to a 

lighter-colored zone or line (especially on longitudinal section), thereby 
appearing sometimes ring-porous; wood hard, heartwood vinous-reddish; 
pith-rays very fine, but very distinct. (See also the sometimes indistinct 
ring-porous cedar-elm, and occasionally winged elm, which are readily 
distinguished by the concentric wavy lines of pores in the summer wood.) 

(No. 57) Cherry. 

C. Pores minute or indistinct, neither conspicuously larger nor more numerous in 

the spring wood and evenly distributed. 

1. Broad pith-rays present. 

a. All or most pith-rays broad, numerous, and crowded, especially on tan¬ 

gential sections, medium heavy and hard, difficult to split. 

(Nos. 112 and 113) Sycamore. 

b. Only part of the pith-rays broad. 

a'. Broad pith-rays well defined, quite numerous; wood reddish white 

to reddish.(No. 47) Beech. 

b'. Broad pith-rays not sharply defined, made up of many small rays, 
not numerous. Stem furrowed, and therefore the periphery 
of section, and with it, the annual rings, sinuous, bending in 
and out, and the large pitli-rays generally limited to the fur¬ 
rows or concave portions. Wood white, not reddish. 

(No. 52) Blue Beech. 


i 

DDITIONAL NOTES FOR DISTINCTIONS IN THE GROUP. 


Cherry and birch are sometimes confounded. The high pith-rays on the cherry on 
radial sections readily distinguish it; distinct pores on birch and spring-wood zone 
in cherry, as well as the darker vinous-brown color of the latter, will prove helpful. 

Two groups of birches can be readily distinguished, though specific distinction is 
not always possible. 

1. Pith-rays fairly distinct, the pores rather few and not more abundant in the 
spring wood; wood heavy, usually darker. 

(No. 48) Cherry-birch and (No. 49) Yellow Birch. 



Beech_1_Sycamore__!_Birch_1 

Fig. 126.—Wood of Beech, Sycamore, and Birch. 




























































































































































TIMBER. 


265 


2, No broad pith-rays present. 

a. Pith-rays small to very small, but quite distinct. 

a'. Wood hard. 

a". Color reddish white, with dark reddish tinge in outer sum¬ 
mer wood.(Nos. 79-82) Maple. 

V. Color white, without reddish tinge.(No. 76) Holly. 

b'. Wood soft to very soft. 

a". Pores crowded, occupying nearly all the space between 
pith-rays. 

a"'. Color yellowish white, often with a greenish tinge 

in heartwood.(No. 115) Tulip-poplar. 

(No. 116) Cucumber-tree. 
V ". Color of sapwood grayish, of heartwood light to 

dark reddish brown.(No. 69) Sweet Gum. 

b". Pores not crowded, occupying not over one third the pith- 
rays; heartwood brownish white to very light brown. 

(Nos. 45 and 46) Basswood. 

b. Pith-rays scarcely distinct, yet if viewed with ordinary magnifier 

plainly visible. 

a'. Pores indistinct to the naked eye. 

a", Color uniform pale yellow; pith-rays not conspicuous even 

on the radial section.(Nos. 53 and 54) Buckeye. 

b". Sapwood yellowish gray, heartwood grayish brown; pith- 
rays conspicuous on the radial section. 

(Nos. 67. 68) Sour Gum. 
b\ Pores scarcely distinct, but mostly visible as grayish specks on the 
cross-section; sapwood whitish, heartwood reddish. 

(Nos. 48-51) Birch. 

3. Pith-rays not visible or else indistinct, even if viewed with magnifier. 

1. Wood very soft, white, or in shades of brown, usually with a silky lustre. 

(Nos. 105-110) Cottonwood (Poplar). 


2. Pith-rays barely distinct, pores more numerous and commonly forming a 
more porous spring-wood zone; wood of medium weight. 

(No. 51) Canoe- or Paper-birch. 
The species of maple may be distinguished as follows: 

1. Most of the pith-rays broader than the pores and very conspicuous. 

(No. 79) Sugar-maple. 


Fig. 127.—Wood of Maple. 



































































































































































































266 


TEE MATERIALS OF CONSTRUCTION. 


additional notes— continued. 


2. Pith-rays not or rarely broader than the pores, fine but conspicuous. 

a. Wood heavy and hard, usually of darker reddish color and commonly 

spotted on cross-section.(No. 80) Red Maple* 

b. Wood of medium weight and hardness, usually light-colored. 

(No. 82) Silver Maple* 

Red maple is not always safely distinguished from soft maple. In box-elder the 
pores are finer and more numerous than in soft maple. 

The various species of elm may be distinguished as follows: 

1. Pores of spring wood form a broad band of several rows; easy splitting, dark 

brown heart..(No. 64) Red Elm* 

2. Pores of spring wood usually in a single row, or nearly so. 

a. Pores of spring wood large, conspicuously so.(No 62) White Elm* 

b. Pores of spring wood small to minute. 

a'. Lines of pores in summer wood fine, not as wide as the interme¬ 
diate spaces, giving rise to very compact grain, 

(No. 63) Rock-elm. 

b\ Lines of pores broad, commonly as wide as the intermediate spaces. 

(No. 66) Winged Elm. 

c. Pores in spring wood indistinct, and therefore hardly a ring-porous 

wood..(No. 65) Cedar-elm. 




SU.W. 


> sp.wr. 


Fig. 129.— Walnut, p. r., pith-rays; 
c. L, concentric lines; v, vessels or 
pores; su. w., summer wood; sp. w. 5 
spring wood. 



Fig. 130.—Wood of Cherry. 





















































































































































































































































































































































TIMBER. 


267 


LIST OF THE MORE IMPORTANT WOODS OF THE UNITED STATES.* 

[Arranged alphabetically.] 

Note. —In the following descriptions the terms expressing size have been used 
with the following meanings : 

Small — trees of 50 feet high or less. 

Medium = “ “ 50 to 100 feet high. 

Large = “ “ over 100 feet in height. 

All these terms must be understood as having been used as approximate estimates only. 

A. CONIFEROUS WOODS. 

Woods of simple and uniform structure, generally light, Soft but stiff; 
abundant in suitable dimensions and forming by far the greatest part of all 
the lumber used. 

222. Cedar.—Light, soft, stiff, not strong, of fine texture; sap and heart- 
wood distinct, the former lighter, the latter a dull grayish brown or red. 
The wood seasons rapidly, shrinks and checks but little, and is very dur¬ 
able. Used like soft pine, but owing to its great durability preferred for 
shingles, etc. Small sizes used for posts, ties, etc. Cedars usually occur 

scattered, but they form, in certain localities, forests of considerable extent. 

« 

a. White Cedars. —Heartwood a light grayish brown. 


1, White Cedar (Thuya occidentalis ) (Arbor- 
vitse): Scattered along streams and lakes, frequently 
covering extensive swamps; rarely large enough for 
lumber, but commonly used for posts, ties, etc. 
Maine to Minnesota and northward. 


Fig. 131.— T. occidentalis, 

2. Canoe-cedar {Thuya gigantm) (red cedar of 
the West): In Oregon and Washington a very large 
tree, covering extensive swamps; in the mountains 
much smaller, skirting the watercourses; an impor¬ 
tant lumber tree. Washington to northern California 
and eastward to Montana. 

T 

Fig. 132. —7’. gigantea. 




* Tlie text here is from U. S. Forestry Bulletin No. 10, while many of the cuts are 
from Apgar’s Trees of the Northern States. The remaining cuts have been specially 
drawn for this work, under the direction of Dr. William Trelease, Director of the Mis¬ 
souri Botanical Garden, St. Louis. 











268 


THE MATERIALS OF CONSTRUCTION 



3. White Cedar (Chamcecyparis thyoides ): 
Medium-sized tree, wood very light and soft. Along 
the coast from Maine to Mississippi. 


Fig. 133. — C. thyoides. 


4. White Cedar {Chamcecyparis Iciwsoniana ) 
(Port Orford cedar, Oregon cedar, Lawsoifis cypress, 
ginger-pine): A very large tree, extensively cut for 
lumber; heavier and stronger than the preceding. 
Along the coast-line of Oregon. 




Fig. 131. — C. Iciwsoniana. 


5. White Cedar (Libocedrus decur- 
rens) (incense-cedar): A large tree, abun¬ 
dantly scattered among pine and fir; 
wood fine-grained. Cascades and Sierra 
Nevada of Oregon and California. 


S tt * 

Fig. 135. — L. decurrens. 



TIMBER. 


269 


b. Red Cedars.— Heartwood red. 

6. Red Cedar (Juniperus virginiana) (Savin juniper): Similar to 
white cedar, but of somewhat finer texture. Used in cabinet work in 
cooperage, for veneers, and especially for lead-pencils, 
for which purpose alone several million feet are cut 
each year. A small to medium-sized tree scattered 
through the forests, or, in the West, sparsely covering 
extensive areas (cedar-brakes). The red cedar is the 
most widely distributed conifer of the United States, 
occurring from the Atlantic to the Pacific and from 
Florida to Minnesota, but attains a suitable size for T 
lumber only in the Southern, and more especially the * IG ’ — ™gini 
Gulf, States. 


7. Redwood {Sequoia sempervirens ): Wood in 
its quality and uses like white cedar; the narrow 
sapwood whitish; the heartwood light red, soon 
turning to brownish red when exposed. A very 
large tree, limited to the coast ranges of Cali¬ 
fornia, and forming considerable forests, which 
are rapidly being converted into lumber. 


Fig. 137.— S. sempervirens. 

223. Cypress. 

8. Cypress (Taxodium distichum ) (bald 
cypress; black, white, and red cypress): Wood in 
appearance, quality, and uses similar to white 
cedar. “ Black cypress 99 and “ white cypress” are 
heavy and light forms of the same species. The 
cypress is a large deciduous tree, occupying much 
of the swamp and overflow land along the coast 
and rivers of the Southern States. 

Fig. 138.— T. distichum. 

224. Fir.—This name is frequently applied to wood and to trees which 
are not fir; most commonly to spruce, but also, especially in English mar¬ 
kets to pine. It resembles spruce, but is easily distinguished from it, as 
well’as from pine and larch, by the absence of resin-ducts. Quality, uses, 

and habits similar to spruce. 








£70 


TUE MATERIALS OF CONSTRUCTION. 



Fig. 139. — A. balsamea. 


9. Balsam-fir ( Abiesbcilsamea ): A medium-sized 
tree scattered throughout the northern pineries; cut, 
in lumber operations, whenever of sufficient size, and 
sold with pine or spruce. Minnesota to Maine and 
northward. 


10. White Fir (Abies grandis and Abies concolor ): Medium to very 


large-sized tree, forming 
an important part of most 
of the Western mountain- 
forests, and furnishing 
much of the lumber of the 
respective regions. The 
former occurs from Van¬ 
couver to central Cali¬ 
fornia and eastward to 
Montana; the latter from 
Oregon to Arizona and 
eastward to Colorado and 
New Mexico. 





11. White Fir (Abies amabilis ): 
Good-sized tree, often forming exten¬ 
sive mountain-forests. Cascade 
Mountains of Washington and Oregon. 


Fig. 142.— A. amabilis. 





































TIMBER. 


271 



13. Bed Fir (Abies magnified)-. Very 
large tree, forming forests about the base 
of Mount Shasta. Sierra Nevada of Cali¬ 
fornia, from Mount Shasta southward. 


Qo ^ 

Fig. 143. — A. nobilis. 


12. Red Fir (Abies nobilis) (not to be con¬ 
founded with Douglas fir; see No. 37): Large to 
very large tree, forming with A. amabilis extensive 
forests on the slope of the mountains between 3000 
and 4000 feet elevation. Cascade Mountains of 
Oregon. 


Fig. 144. — A. magnified. 


225. Hemlock.—Light to medium weight, soft, stiff but brittle, com¬ 
monly cross-grained, rough and splintery; sapwood and heartwood not well 
defined; the wood of a light, reddish-gray color, free from resin-ducts,, 
moderately durable, shrinks and warps considerably, wears rough, retains 
nails firmly. Used principally for dimension stuff and timbers. Hemlocks 
are medium to large-sized trees, commonly scattered among broad-leaved 
trees and conifers, but often forming forests of almost pure growth. 


14. Hemlock (Tsuga canadensis ): Medium¬ 
sized tree, furnishes almost all the hemlock of the 
Eastern market. Maine to Wisconsin; also following 
the Alleghanies southward to Georgia and Alabama. 

























272 


THE MATERIALS OF CONSTRUCTION. 



Fig. 146.— T. mertensiana. 


15. Hemlock (Tsuga mertensiana)'. Large- 
sized tree; wood claimed to be heavier and harder 
than the Eastern form and of superior quality. 
Washington to California and eastward to Mon¬ 
tana. 


226. Larch or Tamarack.—Wood like the best of hard pine both in ap¬ 
pearance, quality, and uses, and, owing to its great durability, somewhat pre¬ 
ferred in ship-building, for telegraph-poles and railroad-ties. In its struc¬ 
ture it resembles spruce. The larches are deciduous trees, occasionally 
covering considerable areas, but usually scattered among other conifers. 


16. Tamarack (Larix americana ) (Hackma¬ 
tack) : Medium-sized tree, often covering swamps, 
in which case it is smaller and of poor quality. 
Maine to Minnesota, and southward to Pennsyl¬ 
vania. 


Fig. 147. — L. americana. 


17. Tamarack (L. occidentalis ): Large-sized trees, 
scattered, locally abundant. Washington and Oregon to 
Montana. 


Fig. 148. — L. occi¬ 
dentalis. 















TIMBER. 


273 


227. Pine.—Very variable, very light and soft in “ soft ” pine, such as 
white pine; of medium weight to heavy and quite hard in “ hard ” pine, of 
which long-leaf or Georgia pine is the extreme form. Usually it is stiff, 
quite strong, of even texture, and more or less resinous. The sapwood is 
yellowish white; the heartwood, orange-brown. Pine shrinks moderately, 
seasons rapidly and without much injury; it works easily; is never too hard 
to nail (unlike oak or hickory); it is mostly quite durable, and if well sea¬ 
soned is not subject to the attacks of boring-insects. The heavier the wood, 
the darker, stronger, and harder it is, and the more it shrinks and checks. 
Pine is used more extensively than any other kind of wood. It is the prin¬ 
cipal wood in common carpentry, as well as in all heavy construction, 
bridges, trestles, etc. It is also used in almost every other wood industry ? 
for spars, masts, planks, and timbers in ship-building, in car and wagon con¬ 
struction, in cooperage, for crates and boxes, in furniture work, for toys and 
patterns, railway-ties, water-pipes, excelsior, etc. Pines are usually large 
trees with few branches, the straight, cylindrical, useful stem forming by 
far the greatest part of the tree; they occur gregariously, forming vast 
forests, a fact which greatly facilitates their exploitation. Of the many 
special terms applied to pine as lumber, denoting sometimes differences in 
quality, the following deserve attention: 

“ White pine,” “pumpkin-pine,” “ soft pine,” in the Eastern markets re¬ 
fer to the wood of the white pine ( Pinas strobus), and on the Pacific Coast 
to that of the sugar-pine (Finns lambertiana). 

“ Yellow pine ” is applied in the trade to all the Southern lumber pines; 
in the Northeast it is also applied to the pitch-pine (P. rigida ); in the West 
it refers mostly to bull-pine ( P. ponderosa). 

“ Yellow long-leaf pine,” “ Georgia pine,” are terms which refer to long- 
leaf pine (P. palustris). 

“Hard pine” is a common term in carpentry, and applies to everything 
except white pine. 

« Pitch-pine” includes all Southern pines and also the true pitch-pine 
(P. rigida), but is mostly applied, especially in foreign markets, to the 
wood of the long-leaf pine ( P . palustris). 

For the great variety of confusing local names applied to the Southern 
pines in their homes, part of which have been adopted in the markets of 
the Atlantic seaboard, see report of Chief of Division of Forestry for 1891, 
page 212, etc., and also the list below. 


274 


THE MATERIALS OF CONSTRUCTION. 


a. Soft Pines. 

18. White Pine [Punts strobus ): Large to very 
large-sized tree; for the last fifty years the most im¬ 
portant timber tree of the Union, furnishing the 
best quality of soft pine. Minnesota, Wisconsin^ 
Michigan, New England, along the Alleghanies to 
Georgia. 


Fig. 149. — P. strobus. 

19. Sugar-pine (Pinus lamberticina): Avery 
large tree, together with Abies concolor , forming 
extensive forests; important lumber tree. Oregon 
and California. 


Fig. 150.— P. lambertiana. 

20. White Pine ( Pinus monticola ): A large 
tree, at home in Montana, Idaho, and the Pacific 
States; most common and locally used in northern 
Idaho. 


Fig. 151.— P. monticola. 

21. White Pine (Pinus flexilis) : A small tree, 
forming mountain-forests of considerable extent 
and locally used; eastern Pocky Mountain slopes; 
Montana to New Mexico. 






Fig. 152. — P. -flexilis. 








TIMBER. 


275 


b. Hard Pines. 

22. Long-leaf Pine (Pinus palustris) 
{Georgia pine, yellow pine, long straw-pine, etc.): 
Large tree; forms extensive forests and furnishes 
the hardest and strongest pine lumber in the mar¬ 
ket. Coast region from North Carolina to Texas. 


Fig. 153.— P. palustris. 

23. Bull-pine (Pinus ponderosa) (yellow 
pine): Medium to very large-sized tree, forming 
extensive forests in Pacific and Rocky Mountain 
regions; furnishes most of the hard pine of the 
West; sap wood wide; wood very variable. 


24. Loblolly Pine (Pinus tcvda) (slash-pine, 
old field-pine, rosemary-pine, sap-pine, short straw- 
pine, etc.): Large-sized tree, forms extensive 
forests; wider-ringed, coarser, lighter, softer, with 
more sapwood than the long-leaf pine, but the two 
often confounded. This is the common lumber 
pine from Virginia to South Carolina, and is 
found extensively in Arkansas and Texas. 
Southern States; Virginia to Texas and Arkansas. 


25. Norway Pine (Pinus resmosa): Large¬ 
sized tree, never forming forests, usually scattered 
or in small groves, together with white pine; largely 
sapwood and hence not durable. Minnesota to 
Michigan; also in New England to Pennsylvania. 





Fig. 154. — P. ponderosa. 



Fig. 156.— P. resinosa. 












270 


TIIE MATERIALS OF CONSTRUCTION. 


26. Short-leaf Pine (Pinus echinnta) 
(slash-pine, Carolina pine, yellow pine, old field- 
pine, etc.): Resembles loblolly pine; often ap¬ 
proaches in its wood the Norway pine. The 
common lumber pine of Missouri and Arkansas. 
North Carolina to Texas and Missouri. 




Fig. 157. — P. echinata. 


27. Cuban Pine (Pinus cubensis) (slash-pine, swamp- 
pine, bastard-pine, meadow-pine): Resembles long-leaf pine, 
but commonly has wider sapwood and coarser grain; does 
not enter the markets to any great extent. Along the 
coast from South Carolina to Louisiana. 


158.— P. cu¬ 
bensis. 

28. Bull-pine (Pinus jeffreyi) 
(black pine): Large-sized tree, wood re¬ 
sembling bull-pine (P. ponderosa); used 
locally in California, replacing P. pon¬ 
derosa at high altitudes. 




F ig. 159. — P. jeffreyi. 

The following are small to medium-sized pines, 
not commonly offered as lumber in the market; 
used locally for timber, ties, etc.: 

29. Black Pine (Pinus murrayana) (lodge- 
pole pine, tamarack): Rocky Mountains and 
Pacific regions. 


rig. ii 


Fig. 160. — P. murrayana . 

















TIMBER. 


277 


30. Pitch-pike (Pinus rigida): Along the 
coast from New York to Georgia, and along the 
mountains to Kentucky. 


Fig. 161.— P. rigida. 

31. Jersey Pike (Pinus inojis) (scrub-pine) r 
As before. 


Fig. 162.— P. inops. 

32. Gray Pike ( Pinus banJcsiana) (scrub- 
pine) : Maine, Vermont, and Michigan to Minne¬ 
sota. 

Redwood. See Cedar. 

228. Spruce.—Resembles soft pine, is light, 

, i • n Fig. 163.— P. banksiana. 

very soft, stiff, moderately strong, less resinous than 

pine; has no distinct heartwood, and is of whitish color. Used like soft 
pine, but also employed as resonance-wood and preferred for paper pulp. 
Spruces, like pines, form extensive forests; they are more frugal, thrive on 
thinner soils, and bear more shade, but usually require a more humid cli¬ 
mate. “ Black ” and “ white ” spruce, as applied by lumbermen, usually 
refer to narrow- and wide-ringed forms of the black spruce (Picea nigra). 

33. Black Spruce ( Picea nigra) : Medium¬ 
sized tree, forms extensive forests in northeastern 
United States and in British America; occurs 
scattered or in groves, especially in low lands 
throughout the Northern pineries. Important 
lumber tree in Eastern United States. Maine to 
Minnesota, British America, and on tiie Allegha— 
nies to North Carolina. 

Fig. 164.— P. nigra. 















278 


THE MATERIALS OF CONSTRUCTION. 


34. White Spruce (Picea alba): Generally 
associated with the preceding; most abundant 
along streams and lakes, grows largest in Mon¬ 
tana, and forms the most important tree of the 
subarctic forest of British America. Northern 
United States, from Maine to Minnesota, also 
from Montana to Pacific, British America. 




Fig. 165.— P. alba. 

35. White Spruce (Picea engelmanni ): 
Medium to large-sized tree, forming extensive 
forests at elevations from 5000 to 10,000 feet 
above sea-level; resembles the preceding, but occu¬ 
pies a different station. A very important timber 
tree in the central and southern parts of the 
Pocky Mountains. Rocky Mountains from Mexico 
to Montana. 


Fig. 166.— P. engelmanni. 

36. Tide-lahd Spruce (Picea sitchensis ): A 
large-sized tree, forming an extensive coast-belt 
forest. Along the seacoast from Alaska to central 
California. 

Bastard Spruce.—Spruce or fir in name, 
but resembling hard pine or larch in the appear¬ 
ance, quality, and uses of its wood. 




P. douglasii. 


Fig. 167.— P. sitchensis. 

37. Douglas Spruce (Pseudotsuga doug¬ 
lasii) (yellow fir, red fir, Oregon pine): One of 
the most important trees of the Western United 
States; grows very large in the Pacific States, 
to fair size in all parts of the mountains, in 
Colorado up to about 10,000 feet above sea- 
level; forms extensive forests, often of pure 
growth. Wood very variable, usually coarse¬ 
grained and heavy, with very pronounced sum¬ 
mer wood, hard and strong (“ red ” fir), but 
often fine-grained and light (“ yellow” fir). It 
replaces hard pine and is especially suited to 
heavy construction. From the plains to the 
Pacific Ocean; from Mexico to British America. 














TIMBER . 


279 



Tamarack, See Larch. 

229. Yew. —Wood heavy, hard, extremely stiff and strong, of fine tex¬ 
ture, with a pale yellow sapwood and an orange- 
red heart; seasons well and is quite durable. 
Yew is extensively used for archery, bows, turn¬ 
er’s ware, etc. The yews form no forests, but 
occur scattered with other conifers. 


38. Yew (Taxus brevifolia ): A small to 
medium-sized tree of the Pacific region. 


Fig. 169.— T. brevifolia. 


B. BROAD-LEAVED WOODS. (HARDWOODS.) 

Woods of complex and very variable structure and therefore differing 
widely in quality, behavior, and consequently in applicability to the arts. 

230. Ash.—Wood heavy, hard, strong, stiff, quite tough, not durable in 
contact with soil, straight-grained, rough on the split surface and coarse in 
texture. The wood shrinks moderately, seasons with little injury, stands 
well and takes a good polish. In carpentry ash is used for finishing lumber, 
stairways, panels, etc.; it is used in ship-building, in the construction of 
cars, wagons, carriages, etc., in the manufacture of farm-implements, 
machinery, and especially of furniture of all kinds, and also for harness 
work; for barrels, baskets, oars, tool-handles, hoops, clothespins, and toys. 
The trees of the several species of ash are rapid growers, of small to medium 
height with stout trunks; they form no forests, but occur scattered in 
almost all our broad-leaved forests. 


39. WniTE Ash (Fraxinus americana ): 
Medium, sometimes large-sized tree. Basin of 
the Ohio, but found from Maine to Minnesota 
and Texas. 



Fig. 170 — F. americana . 








280 


THE MATERIALS OF CONSTRUCTION. 



40. Red Ash (Fraxinus pubescetis): Small-sized 
tree. North Atlantic States, but extends to the 
Mississippi. 


Fig. 171. — F. pubescens. 

41. Black Ash ( Fraxinus sambucifolia) (hoop- 
ash, ground-ash): Medium-sized tree, very common. 
Maine to Minnesota, and southward to Virginia and 
Arkansas. 




Fig. 172. — F. sambuci - 
folia. 

42. Blue Ash (Fraxinus quadrangulata)\ 
Small to medium-sized. Indiana and Illinois; 
occurs from Michigan to Minnesota and southward 
to Alabama. 


Fig. 173. — F. quadrangu- 
lata. 



43. Green Ash ( Fraxinus viridis) : Small¬ 
sized tree. New York to the Rocky Mountains, 
and southward to Florida and Arizona. 


Fig. 174. — F. viridis. 



















TIMBER. 


281 


44. Oregon Ash (Fraxinus or eg ana ): 
Medium-sized tree. Western Washington 
to California. 



Aspen. See Poplar. 
231. Basswood. 



Fig. 176 .—T. americana. 


45. Basswood {Tilia americana) (lime-tree, 
American linden, lin, bee-tree): Wood light, soft, 
stiff but not strong, of fine texture, and white to 
light brown color. The wood shrinks considerably 
in drying, works and stands well; it is used in car¬ 
pentry, in the manufacture of furniture and wood- 
enware, both turned and carved, in cooperage, for 
toys, also for panelling of car and carriage bodies. 
Medium to large-sized tree, common in all Northern 
broad-leaved forests; found throughout the Eastern 
United States. 


46. White Basswood (Tilia lieterophylla ): A 
small-sized tree most abundant in the Alleghany 
region. 



Fig. 177. — T. Itetero - 
phylla. 













282 


THE MATERIALS OF CONSTRUCTION. 


232. Beech. 

47. Beech (F'agus ferruginea ): Wood heavy, hard, stiff, strong, of 

rather coarse texture, white to light brown, not dura¬ 
ble in the ground, and subject to the inroads of 
boring-insects; it shrinks and checks considerably 
in drying, works and stands well, and takes a good 
polish. Used for furniture, in turnery, for handles, 
lasts, etc. Abroad it is very extensively employed 
by the carpenter, millwright, and wagon-maker, in 
turnery as well as wood-carving. The beech is a 
medium-sized tree, common, sometimes forming for¬ 
ests; most abundant in the Ohio and the Mississippi 
basin, but found from Maine to Wisconsin and 
Fig. 178.— F. ferruginea. southward to Florida. 

233. Birch.—Wood heavy, hard, strong, of fine texture ; sapwood whit¬ 
ish, heartwood in shades of brown with red and yellow; very handsome, 
with satiny lustre, equalling cherry. The wood shrinks considerably in dry¬ 
ing, works and stands well and takes a good polish, but is not durable if 
exposed. Birch is used for finishing-lumber in building, in the manufac¬ 
ture of furniture, in wood-turnery for spools, boxes, wooden shoes, etc., for 
shoe lasts and pegs, for wagon-hubs, ox-yokes, etc., also in wood-carving. 
The birches are medium-sized trees, form extensive forests northward, and 
occur scattered in all broad-leaved forests of the Eastern United States. 



48. Cherry-birch (Betula lento) (black birch, 
sweet birch, mahogany-birch): Medium-sized tree; 
very common. Maine to Michigan and to Tennessee. 




Fig. 179.— B. lenta . 

49. Yellow Birch (Betula lutea) (gray 
birch): Medium-sized tree; common. Maine to 
Minnesota and southwest to Tennessee. 


Fig. 180.— B. lutea. 












TIMBER. 


283 


50. Red Birch (Betula nigra) (river-birch): 
Small to medium-sized tree; very common; lighter 
and less valuable than the preceding. New England 
to Texas and Missouri 


Fig. 181.— B. nigra. 

51. Canoe-birch (Betula papyrifera) (white 
birch, paper-birch): Generally a small tree; common, 
forming forests; wood of good quality, but relatively 
light. All along the northern boundary of United 
States and northward, from the Atlantic to the Pacific. 


Fig. 182.— B. papy- 
rifera. 

Black Walnut. See Walnut. 

234. Blue Beech. 

52. Blue Beech (Carpinuscaroliniana) (horn¬ 
beam, water-beech, ironwood): Wood very heavy, 
hard, strong, very stiff, of rather fine texture and 
white color; not durable in the ground; shrinks 
and checks greatly, but works and stands well. 
Used chiefly in turnery for tool-handles, etc. 
Abroad much used by millwrights and wheel¬ 
wrights. A small tree, largest in the Southwest, 
but found in nearly all parts of the Eastern United 
States. 





Fig. 183. — C. caroliniana. 


Bois d’Arc. See Osage Orange. 

235. Buckeye—Horse-Chestnut. —Wood light, soft, not strong, often 
quite tough, of fine and uniform texture and creamy-white color. It shrinks 
considerably, but works and stands well. Used for wooden ware, artificial 
limbs, paper-pulp, and locally also for building-lumber. Small-sized trees, 
scattered. 










'284 


THE MATERIALS OF CONSTRUCTION. 



53. Ohio Buckeye (JEsculus glabra) (fetid buckeye): 
Alleghanies, Pennsylvania to Indian Territory. 


Fig 184. 
FE. glabra. 


54. Sweet Buckeye (FEsculus flava)\ Alle¬ 
ghanies, Pennsylvania to Texas. 



236. Butternut. 


Fig 185.— jE. flava. 



Fig. 186. — J. cinerea . 


55. Butternut (Juglans cinerea) (white 
walnut): Wood very similar to black walnut, 
but light, quite soft, not strong, and of light- 
brown color. Used chiefly for finishing lumber, 
cabinetwork, and cooperage. Medium-sized 
tree, largest and most common in the Ohio 
basin; Maine to Minnesota and southward to 
Georgia and Alabama. 


237. Catalpa. 



Fig. 187. — C. speciosa. 


56. Catalpa (Catalpa speciosa): Wood light, 
soft, not strong, brittle, durable, of coarse texture 
and brown color; used forties and posts, but well 
suited for a great variety of uses. Medium-sized 
trees; lower basin of the Ohio River, locally com¬ 
mon. Extensively planted, and therefore promising 
to become of some importance. 
















TIMBER. 


285 


238. Cherry. 

57. Cherry ( Prunus serotina): Wood heavy, hard, strong, of fine tex¬ 
ture; sapwood yellowish white, heartwood reddish to brown. The wood 
shrinks considerably in drying, works and stands well, takes a good polish, 
and is much esteemed for its beauty. Cherry is 
chiefly used as a decorative finishing-lumber for 
buildings, cars, and boats, also for furniture and in 
turnery. It is becoming too costly for many ^purposes 
for which it is naturally well suited. The lumber¬ 
furnishing cherry of this country, the wild black 
cherry ( Prunus serotina ), is a small to medium-sized 
tree, scattered through many of the broad-leaved 
woods of the western slope of the Alleghanies, but FlG * serotina. 

found from Michigan to Florida and west to Texas. Other species of this 
genus as well as the hawthorns (Cratcegas) and wild apple ( Pyrus ) are not 
commonly offered in the market. Their wood is of the same character as 
cherry, often even finer, but in small dimensions. 



239. Chestnut. 



Fig. 189.— C. vulgaris. 


58. Chestnut ( Castanea vulgaris var. ameri - 
cana): Wood light, moderately soft, stiff, not strong, 
of coarse texture; the sapwood light, the heartwood 
darker brown. It shrinks and checks considerably 
in drying, works easily, stands well, and is very dura¬ 
ble. Used in cabinetwork, cooperage, for railway-ties, 
telegraph-poles, and locally in heavy construction. 
Medium-sized tree, very common in the Alleghanies, 
occurs from Maine to Michigan and southward to 
Alabama. 


59. Chinquapin (Castanea pumila): A small-sized 
tree, with wood slightly heavier than, but otherwise sim¬ 
ilar to, the preceding; most common in Arkansas, but 
with nearly the same range as the chestnut. 



Fig. 190. — G. pumila. 





















286 


TEE MATERIALS OF CONSTRUCTION. 


GO. Chinquapin (Castanopsis chryso 
phylla ): A medium-sized tree of the west 
ern ranges of California and Oregon. 


Fig. 191.— C. chrysophylla. 

61. Coffee-tree (Gymnodadus eanaclensis ) 
(coffee-nut): Wood heavy, hard, strong, very stiff, of 
coarse texture; durable; the sapwood yellow, the 
heartwood reddish brown; shrinks and checks con¬ 
siderably in drying; works and stands well and takes 
a good polish. It is used to a limited extent in cab¬ 
inetwork. A medium to large-sized tree; not com¬ 
mon. Pennsylvania to Minnesota and Arkansas. 


Cottonwood. See Poplar. 

Cucumber-tree. See Tulip. 

241. Elm.—Wood heavy, hard, strong, very tough : moderately durable in 
contact with the soil; commonly cross-grained, difficult to split and shape, 
warps, and checks considerably in drying, but stands well if properly han¬ 
dled. The broad sapwood whitish, heart brown, both with shades of gray 
and red; on split surface rough; texture coarse to fine; capable of high 
polish. Elm is used in the construction of cars, wagons, etc., in boat- and 
ship-building, for agricultural implements and machinery ; in rough cooper¬ 
age, saddlery and harness work, but particularly in the manufacture of all 
kinds of furniture, where the beautiful figures, especially those of the tan¬ 
gential or bastard section, are just beginning to be duly appreciated. The 
elms are medium to large-sized trees, of fairly rapid growth, with stout trunk, 
form no forests of pure growth, but are found scattered in all the broad¬ 
leaved woods of our country, sometimes forming a considerable portion of 
the arborescent growth. 




r 








TIMBER. 


287 



62. White-elm (Ulmus americanct) (American 
elm, water-elm): Medium to large-sized tree, com¬ 
mon. Maine to Minnesota, southward to Florida 
and Texas. 


Fig. 193.— U. americana. 

63. Rock-elm (Ulmus racemosa ) (cork-elm, 
hickory-elm, white elm, cliff-elm): Medium to large¬ 
sized tree. Michigan, Ohio, from Vermont to Iowa, 
southward to Kentucky. 




Fig. 194.— U. racemosa. 


64. Red Elm (Ulmus fulva) (slippery elm >; 
moose-elm): Small-sized tree, found chiefly along 
watercourses. New York to Minnesota, and south¬ 
ward to Florida and Texas. 


Fig. 195.— U. fulva. 


65. Cedar-elm (Ulmus crassifolia ): 
Small-sized tree, quite common. Arkansas 
and Texas. 



Fig. 196.— U. crassifolia 






































288 


THE MATERIALS OF CONSTRUCTION. 



Fig. 197.— U. alata. 


66. Winged Elm (Ulmus alata) (Walioo): 
Small-sized tree, locally quite common. Arkan¬ 
sas, Missouri, and eastern Virginia. 


242. Gum.—This general term refers to two kinds of wood usually dis¬ 
tinguished as sweet or red gum, and sour, black, or tupelo gum, the former 
being a relative of the witch-hazel, the latter belonging to the dogwood 
family. 



Fig. 198.—A. sylvatica. 


67. Tupelo (Nyssa sylvatica) (sour gum, black 
gum): Maine to Michigan, and southward to Flor¬ 
ida and Texas. Wood heavy, hard, strong, tough, 
of fine texture, frequently cross-grained, of yellowish 
or grayish-white color, hard to split and work, 
troublesome in seasoning, warps and checks consid¬ 
erably, and is not durable if exposed; used for wagon- 
hubs, wooden ware, handles, wooden shoes, etc. 
Medium to large-sized trees, with straight, clear 
trunks; locally quite abundant, but never forming 
forests of pure growth. 


68. Tupelo Gum (Nyssa uniflora) (cotton- 
gum): Lower Mississippi basin, northward to Illi¬ 
nois and eastward to Virginia; otherwise like pre¬ 
ceding species. 



Fig. 199,— N. uniflora. 















TIMBER. 


289 


69. Sweet Gum (Liquidambar styracifiua) (red gum, liquidambar, 



bilsted): Wood rather heavy, rather soft, quite stiff 
and strong, tough, commonly cross-grained, of fine 
texture; the broad sapwood whitish, the heart- 
wood reddish brown; the wood shrinks and warps 
considerably, but does not check badly, stands well 
when fully seasoned, and takes good polish. Sweet 
gum is used in carpentry, in the manufacture of fur¬ 
niture, for cut veneer, for wooden plates, plaques, 
baskets, etc., also for wagon-hubs, hat-blocks, etc. 


* 1^V7 A large-sized tree, very abundant, often the princi- 

V ^ pal tree in the swampy parts of the bottoms of the 

Fig. 200. — L. styracifiua. Lower Mississippi Valley; occurs from New York 
to Texas, and from Indiana to Florida. 

243. Hackberry. 

70. Hackberry (Celtisoccidentalis) (sugar-berry): 

The handsome wood heavy, hard, strong, quite tough, 
of moderately fine texture, and greenish- or yellowish- 
white color; shrinks moderately, works well, and takes 
a good polish. So far but little used in the manufac¬ 



ture of furniture. Medium to large-sized tree, locally 


quite common, largest in the Lower Mississippi Valley; Fig 201 — (7 occiden- 
occurs in nearly all parts of the Eastern United States. talis. 

244. Hickory.—Wood very heavy, hard, and strong, proverbially tough, 
of rather coarse texture, smooth and of straight grain. The broad sapwood 
white, the heart reddish nut-brown. It dries slowly, shrinks and checks 
considerably; is not durable in the ground, or if exposed, and especially the 
sapwood, is always subject to the inroads of boring-insects. Hickory excels 
as carriage and wagon stock, but is also extensively used in the manufacture 
of implements and machinery, for tool-handles, timber-pins, for harness 
work and cooperage. The hickories are tall trees with slender stems, never 
form forests, occasionally small groves, but usually occur scattered among 
other broad-leaved trees in suitable localities. The following species all 
contribute more or less to the hickory of the markets: 



common; the favorite among hickories; best devel- 
<7 oped in the Ohio and Mississippi basins; from Lake 
Ontario to Texas, Minnesota to Florida. 


71. Shagbark Hickory ( Hicoria ovata ) (shell- 
bark hickory): A medium to large-sized tree, quite 


Fig 202.— II. ovata. 





290 


THE MATERIALS OF CONSTRUCTION. 



Fig. 204.— H. glabra. 


74. Bitter-nut Hickory (Hicoria minima) 
(swamp hickory): A medium-sized tree, favoring 
wet iocalities, with the same range as the preceding. 


Fig. 205.— H. minima. 


75. Pecan (Hicoria pecan) (Illinois nut): A 
large tree, very common in the fertile bottoms of the 
Western streams. Indiana to Nebraska and south¬ 
ward to Louisana and Texas. 


Fig. 206.— II. pecan. 


Fig. 203.— H alba. 


73. Pignut Hickory (Hicoria glabra) 
(brown hickory, black hickory, switch-bud hick¬ 
ory): Medium to large-sized tree, abundant; all 
Eastern United States. 


77. Mockernut Hickory (Hicoria alba) (black 
hickory, bull-and black-nut, big-bud, and white-heart 
hickory): A medium to large-sized tree, with the same 
range as the foregoing; common, especially in the 
South. 












TIMBER. 


291 


245. Holly. 

76. Holly (Ilex opaca ): Wood of medium weight, 
hard, strong, tough, of fine texture and white color; 
works and stands well, used for cabinetwork and turnery. 
A small tree, most abundant in the Lower Mississippi 
Valley and Gulf States, but occurring eastward to Massa¬ 
ge- 207.—/ opaca. chusetts and north to Indiana. 

Horse-chestnut. See Buckeye. 

Ironwood. See Blue Beech. 

246. Locust. —This name applies to both of the following: 

77. Black Locust ( Robinia pseudacacia) (black locust, yellow locust): 

Wood very heavy, hard, strong, and tough, of 
coarse texture, very durable in contact with the 
soil, shrinks considerably, and suffers in season¬ 
ing; the very narrow sapwood yellowish, the 
heartwood brown, with shades of red and green. 
Used for wagon-hubs, treenails or pins, but espe¬ 
cially for ties, posts, etc. Abroad it is much used 
for furniture and farm-implements, and also in 
turnery. Small to medium-sized tree, at home in 
the Alleghanies, extensively planted, especially 
in the West. 

78. Honey-locust ( Gleditschia triacanthos ) 

(black locust, sweet locust, three-thorned acacia): 

Wood heavy, hard, strong, tough, of coarse texture, 
susceptible of a good polish, the narrow sapwood yel¬ 
low, the heartwood brownish red. So far but little 
appreciated except for fencing and fuel; used to some 
extent for wagon-hubs and in rough construction. 

A medium-sized tree, found from Pennsylvania to 
Nebraska, and southward to Florida and Texas; lo- Fig. 209.— O. triacanthos. 

cally quite abundant. 

Magnolia. See Tulip. 

247. Maple. —Wood heavy, hard, strong, stiff, and tough, of fine texture, 
frequently wavy-grained, this giving rise to “ curly ” and “blister” figures; 
not durable in the ground or otherwise exposed. Maple is creamy white, 
with shades of light brown in the heart; shrinks moderately, seasons, works 
and stands well, wears smoothly, and takes a fine polish. The wood is used 
for ceiling, flooring, panelling, stairway, and other finishing-lumber in house, 
ship, and car construction; it is used for the keels of boats and ships, in the 
manufacture of implements and machinery, but especially for furniture, 
where entire chamber sets of maple rival those of oak. Maple is also used 




Fig. 208. — R. pseudacacia. 






292 


THE MATERIALS OF CONSTRUCTION. 


for shoe-lasts and other form-blocks, for shoe-pegs, for piano actions, school 
apparatus, for wood type in show-bill printing, tool-handles, in wood-carv¬ 
ing, turnery, and scrollwork. The maples are medium-sized trees, of fairly 
rapid growth; sometimes form forests and frequently constitute a large pro¬ 
portion of the arboresoent growth. 

79. Sugar-maple (Acer saccharum) (hard 
maple, rock-maple): Medium to large-sized tree, 
very common, forms considerable forests. Maine 
to Minnesota, abundant, with birch, in parts of 
the pineries; southward to northern Florida; 
most abundant in the region of the Great Lakes. 


Fig. 210.— A. saccharum. 

80 . Red Maple (Acer ruhrum ) (swamp- or water- 
maple) : Medium-sized tree. Like the preceding, but 
scattered along watercourses and other moist localities. 


Fig. 211.— A. rubrum. 

81. Silver Maple (Acer saccliarinum ) (soft 
maple, silver maple): Medium-sized, common; wood 
lighter, softer, inferior to hard maple, and usually 
offered in small quantities and held separate in the 
market. Valley of the Ohio, but occurs from Maine 
o Dakota, and southward to Florida. 


num. 

82 . Broad-leaved Maple (Acer macropliyl- 
lum ): Medium-sized tree, forms considerable 
forests, and like the preceding has a lighter, 
softer, and less valuable wood. Pacific Coast. 




Fig. 212.— A . sacchari - 




Fig. 213.— A. macrophyllum. 












TIMBER. 


293 


248. Mulberry. 

83. Red Mulberry {Morns rubra): Wood moderately 
heavy, hard, strong, rather tough, of coarse texture, dur¬ 
able; sapwood whitish, hard yellow to orange-brown; 
shrinks and checks considerably in drying; works and 
stands well. Used in cooperage and locally in ship-build¬ 
ing and in the manufacture of farm-implements. A small¬ 
sized tree, common in the Ohio and Mississippi valleys, 
but widely distributed in the Eastern United States. 

249. Oak.—Wood very variable, usually very heavy and hard, very strong 
and tough, porous, and of coarse texture; the sapwood whitish, the heart 
“ oak ” brown to reddish brown. It shrinks and checks badly, giving trouble 
in seasoning, but stands well, is durable, and little subject to attacks of in¬ 
sects. Oak is used for many purposes: in ship-building, for heavy construc¬ 
tion, in common carpentry, in furniture, car, and wagon work, cooperage, 
turnery, and even in wood-carving; also in the manufacture of all kinds of 
farm-implements, wooden mill machinery, for piles and wharves, railway- 
ties, etc. The oaks are medium to large-sized trees, forming the predomi¬ 
nant part of a large portion of our broad-leaved forests, so that these are 
generally “ oak forests,” though they always contain a considerable propor¬ 
tion of other kinds of trees. Three well-marked kinds, white, red, and live 
oak, are distinguished and kept separate in the market. Of the two princi¬ 
pal kinds white oak is the stronger, tougher, less porous, and more durable. 
Red oak is usually of coarser texture, more porous, often brittle, less dura¬ 
ble, and even more troublesome in seasoning than white oak. In carpen¬ 
try and furniture work red oak brings about the same price at present as 
white oak. The red oaks everywhere accompany the white oaks, and, like 
the latter, are usually represented by several species in any given locality. 
Live-oak, once largely employed in ship-building, possesses all the good 
qualities (except that of size) of white oak even to a greater degree. It is 
one of the heaviest, hardest, and most desirable building-timbers of this 
country; in structure it resembles the red oaks, but is much less porous. 



Fig. 214 — M. ru¬ 
bra. 



84. WniTE Oak ( Quercus alba): Medium to 
large-sized tree, common in the Eastern States, 
Ohio and Mississippi valleys; occurs throughout 
Eastern United States. 





294 


THE MATERIALS GF CONSTRUCTION. 


85. Bur -oak (Quercus macro carp a) 
(mossy-cup oak, over-cup oak): Large-sized 
tree, locally abundant, common. Bottoms 
west of Mississippi; range farther west than 
preceding. 


8G. Swamp White Oak (Quercus bicolor): 
Large-sized tree, common. Most abundant in the 
Lake States, but with range as in white oak. 


Fig. 217. — Q. bicolor. 

87. Yellow Oak ( Quercus prinoides) (chestnut-oak, chin¬ 
quapin oak): Medium-sized tree. Southern Alleghanies, east¬ 
ward to Massachusetts. 

Fig. 218. 

Q. prinoides. 


88. Basket-oak ( Quercus michauxii) (cow- 
oak): Large-sized tree, locally abundant; lower 
Mississippi and eastward to Delaware. 


Fig. 219.—$. michauxii. 






Fig. 216. — Q. macrocarpa. 


89. Over-cup Oak ( Quercus lyrata ) (swamp white 
oak, swamp post-oak): Medium to large-sized tree, 
rather restricted; ranges as in the preceding. 



Fig. 220. — Q. lyrata. 


















TIMBER. 


295 




90. Post-oak (Quercus obtusiloba) (iron- 
oak) : Medium to large-sized tree. Arkansas 
to Texas, eastward to New England, and 


northward to Michigan. 


Fig. 221. — Q. obtusiloba. 


91. White Oak (Quercus durandii): Medium to 
small-sized tree. Texas, eastward to Alabama. 




Fig. 222. — Q. du¬ 
randii. 


92. White Oak (Quercus garryana ): Medium to 
large-sized tree. Washington to California. 


Fig. 223.— Q . 
garryana . 


93. White Oak (Quercus lobata ): Medium to 
large-sized tree; largest oak on the Pacific coast. I 
California. 



Fig. 224.—Q. lobata . 












296 


THE MATERIALS OF CONSTRUCTION. 


94. Red Oak (Quercus rubra) (black oak): 
Medium to large-sized tree; common in all parts of 
its range. Maine to Minnesota, and southward to 
the Gulf. 

Fig. 225 .— Q. rubra. 

95. Black Oak (Quercus tinctoria ) (yellow 
oak): Medium to large-sized tree; very common in 
the Southern States, but occurring north as far as 
Minnesota, and eastward to Maine. 


96. Spanish Oak (Quercus falcata) (red oak): 
Medium-sized tree; common in the South Atlantic 
and Gulf region, but found from Texas to New 
York, and north to Missouri and Kentucky. 


Fig. 227 .— Q. falcata. 

97. Scarlet Oak (Quercus coccinea ): Me¬ 
dium to large-sized tree; best developed in the 
lower basin of the Ohio, but found from Maine 
to Missouri, and from Minnesota to Florida. 


Fig. 228 . — Q. coccinea . 

98. Pin-oak (Quercus palustris) (swamp Spanish 
oak, water-oak): Medium to large-sized tree, common 
along borders of streams and swamps. Arkansas to Wis¬ 
consin, and eastward to the Alleghanies. 

Fig. 229.—$. palus¬ 
tris. 






Fig. 220 . — Q. tinctoria. 






















TIMBER. 


297 


99. Willow-oak (Quercus phellos) (peach-oak): 
Small to medium-sized tree. New York to Texas, 
and northward to Kentucky. 




Fig. 230.—(). phellos . 


100. Water-oak (Quercus aquatica) (duck-oak, 
possum-oak, punk-oak): Medium to large-sized tree, 
of extremely rapid growth. Eastern Gulf States, east¬ 
ward to Delaware, and northward to Missouri and 
Kentucky. 


Fig. 231. — Q. aquatica. 


101. Live-oak (Quercus virens ): Small-sized tree, 
scattered along the coast from Virginia to Texas. 




Fig. 232.— Q . virens . 


102. Live-oak (Quercus 
chrysolepis) (manl-oa k, 
Valparaiso oak): Medium- 
sized tree. California. 


Fig. 233.—C- chrysolepis . 










298 


THE MATERIALS OF CONSTRUCTION. 


250. Osage Orange. 

103. Osage Orange (Maclura aurantiaco) (Bois d'A'rc): Wood very 
heavy, exceedingly hard, strong, not tough, of 
moderately coarse texture, and very durable; sap- 
wood yellow, heart brown on the end, yellow on 
longitudinal faces, soon turning grayish brown if 
exposed; it shrinks considerably in drying, but 
once dry it stands unusually well. Formerly much 
used for wheel stock in the dry regions of Texas; 
otherwise employed for posts, railway-ties, etc. 

Seems too little appreciated; it is well suited for 
turned ware and especially for wood-carving. A 
small-sized tree, of fairly rapid growth, scattered 
through the rich bottoms of Arkansas and Texas. 

251. Persimmon. 



Fig. 234.— M . aurantiaca 


104. Persimmon (Diospyros virginiana ): Wood 
very heavy and hard, strong and tough; resembles 
hickory, but is of finer texture; the broad sapwood 
cream-color, the heart black; used in turnery for 
shuttles, plane-stocks, shoe-lasts, etc. Small to 
medium-sized tree, common and best developed in 
the Lower Ohio Valley, but occurs from New York 
to Texas and Missouri. 


252. Poplar and Cottonwood. (See also Tulip-wood.) —Wood light, 
very soft, not strong, of fine texture and whitish, grayish, to yellowish color, 
usually with a satiny lustre. The wood shrinks moderately (some cross- 
grained forms warp excessively), but checks little; is easily worked, but is 
not durable. Used as building- and furniture-lumber, in cooperage for 
sugar- and, flour-barrels, for crates and boxes (especially cracker-boxes), for 
woodenware and paper-pulp. 

105. Cottonwood (Populuo monilifera ): Large¬ 
sized tree; forms considerable forests along many of 
the Western streams, and furnishes most of the 
cottonwood of the market. Mississippi Valley and 
west; New England to the Rocky Mountains. 




Fig. 235. — D . virginiana . 


Fig. 236. — P . monilifera . 



















TIMBER. 


299 



106. Balsam ( Populus balsamifera) (balm of 
Gilead): Medium to large-sized tree; common all 
along the northern boundary of the United States. 


Fig. 237. — P. balsamifera. 

107. Black Cottonwood (Populus trichocarpa ): 
The largest deciduous tree of Washington; very common. 
Northern Rocky Mountains and Pacific region. 


Fig. 238. 

P. trichocarpa. 

108. Cottonwood (Populus fre- 
montii var. wislizeni ): Medium to large¬ 
sized tree, common. Texas to Cali¬ 
fornia. 


Fig. 239. — P . wislizeni . 



109. Poplar (Populus grandidentata ): Medium¬ 
sized tree, chiefly used for pulp. Maine to Minne¬ 
sota and southward along the Alleghanies. 


Fig. 240. 

P. grandidentata. 











300 


THE MATERIALS OF CONSTRUCTION'. 



P. tremuloides. 

Sour Gum. 
Red Gum. 
253. Sassafras. 

111. Sassafras 


110. Aspen ( Populus tremuloides ): Small to 
medium-sized tree, often forming extensive forests 
and covering burned areas. Maine to V ashington 
and northward, south in the Western mountains to 
California and New Mexico. 

See Gum. 

See Gum. 



Fig. 242.—S. sassafras. 


(Sassafras sassafras): Wood 
light, soft, not strong, brittle, of coarse texture, 
durable; sapwood yellow, heart orange - brown. 

Used in cooperage, for skill's, fencing, etc. 

Medium-sized tree, largest in the Lower Mississippi 
Valiev, from New England to Texas, and from 
Michigan to Florida. 

Sweet Gum. See Gum. 

254. Sycamore. 

112. Sycamore (. Platanus occidental^) (button-wood, buttonball-tree, 

water-beech): Wood moderately heavy, quite hard, 
stiff, strong, tough, usually cross-grained, of coarse 
texture, and white to light-brown color; the wood 
is hard to split and work, shrinks moderately, 
warps and checks considerably, but stands well. 
It is used extensively for drawers, backs, bottoms, 
etc., in cabinetwork, for tobacco-boxes, in cooper¬ 
age, and also for finishing lumber, where it has 
too long been underrated. A large tree, of rapid 
growth, common and largest in the Ohio and Mis¬ 
sissippi valleys, at home in nearly all parts of the 
Eastern LTnited States. The California species— 

113. Platanus racemosa — resembles in its 



Fig. 243.— P. occidentals. 


wood the Eastern form. 

255. Tulip-wood. 

114. Tulip - tree ( Liriodendron tulipifera) 
(yellow poplar, white wood): Wood quite varia¬ 
ble in weight, usually light, soft, stiff but not 
strong, of fine texture and yellowish color; the 
wood shrinks considerably, but seasons without 
much injury; works and stands remarkably well. 
Used for siding, for panelling and finishing-lum¬ 
ber in house-, car-, and ship-building, for side¬ 
boards and panels of wagons and carriages; also 
in the manufacture of furniture, implements, and 
machinery, for pump-logs, and almost every kind 


o 



Fig. 244.— L. tulipifera. 






TIMBER. 


301 


of common woodenware, boxes, shelving, drawers, etc. An ideal wood for 
the carver and toyman. A large tree, does not form forests, but is quite 
common, especially in the Ohio Basin; occurs from New England to 
Missouri and southward to Florida. 



Fig. 245.— M. acuminata. 


115. Cucumber - tree (Magnolia acumi¬ 
nata) : A medium-sized tree, most common in 
the southern Alleghanies, but distributed from 
New York to Arkansas, southward to Alabama, 
and northward to Illinois. Resembling, and 
probably confounded with, tulip-wood in the 
markets. 


Tupelo. See Gum. 

256. Walnut. 

116. Black Walnut (Juglans nigra): Wood heavy, hard, strong, of 
coarse texture; the narrow sap wood whitish, the 
lieartwood chocolate-brown. The wood shrinks 
moderately in drying, works and stands well, 
takes a good polish, is quite handsome, and has 
been for a long time the favorite cabinet-wood in 
this country. Walnut, formerly used even for 
fencing, has become too costly for ordinary uses, 
and is to-day employed largely as a veneer, for 
inside finish and cabinetwork; also in turnery, for 
gunstocks, etc. Black walnut is a large tree, with 
stout trunk, of rapid growth, and was formerly 
quite abundant throughout the Alleghany region, 
occurring from New England to Texas, and from 
Michigan to Florida. 

White Walnut. See Butternut 



Fig. 246.—/. nigra . 


White Wood. See Tulip, and also Basswood. 

Yellow Poplar. See Tulip. 









PART III. 


TESTING-MACHINES AND METHODS OF TESTING 
MATERIALS OF CONSTRUCTION 


CHAPTER XIV. 

MECHANICAL TESTS IN GENERAL. 

257. General Observations.— Mechanical tests are those most commonly 
used to discover the working qualities of the materials of construction. 
Since these materials nearly always have to resist the action of external 
forces, it follows that the suitableness of such a material to resist the action 
of these forces is best determined by tests approximating as nearly as may 
be to the conditions of actual practice. 

Mechanical tests, therefore, are of supreme importance in the study of 
any building material. By standardizing the conditions under which these 
tests are carried out, the results become comparable wherever or by whom¬ 
soever they are made, and they also become authoritative in all countries 
and for all purposes. If such results can be made wholly independent of 
the means employed in making the tests, and hence to furnish a knowledge 
of the true characteristics of the material, they can be used safely in theo¬ 
retical generalizations on the one hand, and in the practical designing of 
structures on the other. With many kinds of tests this ideal divorcement 
of the results from the conditions of the tests can certainly never bo 
attained, asdn the case of tests by impact, but it doubtless can be practically 
attained in some of the more simple tests, as in tension and .compression. 
In the former case the most that can be accomplished is to prescribe uniform 
conditions in order that the results obtained by different experimenters may 
be comparable, although they may not serve for accurate scientific general¬ 
izations. They might also serve to give a relative value to the various 
materials or samples so tested, and to grade them with some degree of ap¬ 
proximation to their true relative merits for a proposed purpose. Such 
tests, therefore, may serve fully their immediate object even though the 

302 



MECHANICAL TESTS IN GENERAL. 


303 


results can be given no absolute significance whatever. If, however, the 
conditions of such tests are allowed to vary, they would lose even this rela¬ 
tive significance, and would therefore be quite worthless. The standardiz¬ 
ing of any particular kind of test evidently depends on the state of the science 
at the time; and as our knowledge of any particular property of a material 
increases, it is probable that our standard methods of testing will also have 
to change. No such standards, therefore, can be fixed permanently, but 
certain methods can be agreed on and followed for a time, and when a change 
is made let all change together. To attain to this kind of unity of action 
it is necessary to have a world’s representative body which will command 
the confidence and allegiance of both the theoretical and the practical users 
of materials in all civilized countries to decide such questions. A beginning 
has been made in this direction in the International Commission on the 
Standardization of Methods of Testing the Materials of Construction, which 
has had several meetings in Europe at intervals of about three years, the 
last one being at Zurich in September, 1895, where a permanent organiza¬ 
tion was effected. The French Government, also (in 1891, as a result of 
action taken by engineers at their centennial exposition in 1889), appointed 
a national French Commission of over one hundred of the leading authorities 
in France to report on this subject. Their report, printed in four quarto 
volumes (1895), is to-day (1897) by far the best single source of information 
on these subjects. They have proposed what appeared to them practicable 
standard tests for nearly all kinds of structural materials. 

Evidently no complete standardization can be effected for tests on entire 
structural forms, since these vary in shape, size, and disposition of parts, 
but specimen tests can be standardized since all significant conditions can be 
made uniform. 

258. Mechanical Tests Classified. —In a general way we may divide 
mechanical tests of building materials into the following classes: 

With reference to the method of applying the loads we have— 

(1) Static Tests , or those made with gradually increasing loads, such as 
the ordinary tests in tension, compression, cross-bending, torsion, and shear¬ 
ing. 

(2) Dynamic Tests , or those made with suddenly applied loads, as by a 
falling weight. 

(3) Wearing Tests , or those made for determining resistance to abrasion 
and impact, as in the case of paving-materials. 

With reference to the character of the test specimen we have— 

(1) Specimen Tests, or those made upon specimens of the material 
specially prepared and given standard forms and dimensions. 

(2) Structural Tests , or those made on full-sized structural forms, as 
bridge members, brick piers, pipes, wire ropes, chains, riveted joints, etc., 
or on the structure as a whole, such as boilers, simple trusses, frames, and 
various parts of machines. 

Oomnlete standard rules for making tests of structural materials can be 


304 


THE MATERIALS OF CONSTRUCTION. 


adopted for making all kinds of tests on specially prepared specimens, but 
they can be only partially prescribed for tests of structural forms. 

259. General Remarks on Testing-machines.—The following considera¬ 
tions apply to testing-machines and testing-appliances in general: 

1. The weighing apparatus should be quite independent of the loading 
apparatus, the former usually being fixed and the latter movable. 

2. In lever machines the length of the knife-edges must be proportioned 
to the maximum loads in order not to be crushed down, and they should be 
so placed that all will receive their share of the load. They must also be so 
mounted as not to change the leverage by any reaction displacement which 
may occur To insure this, the knife-edges must be attached to the levers, 
and the bearings to the platform. 

3. The knife-edges and bearings of any beam must lie in the same 
straight line, and this line should lie in the gravity axis of the beam and its 
rigid attachments. This is especially necessary for the weighing-beam itself, 
so that its vertical angular movement may not disturb the counterbalancing. 
If the poise is moved by a cord over a pair of pulleys, this cord should be 
attached to the poise-hanger in this same axial line, so that the pulling of 
the poise may not supply a leverage on the beam to raise or lower it. 

4. Manometer machines have many peculiar errors. For example, any 
air-bubble in the indicating liquid vitiates the results by its own change in 
volume under pressure. Again, the exact area of surface subjected to pres¬ 
sure is always uncertain. 

5. The weighing apparatus should be so constructed as to be readily 
verified by the imposition of known weights, and the parts should be open 
to inspection and easily repaired and kept in order. 

G. A precision of 1 in 250 has been considered sufficient.* This is a 
proportional error of 0.4 of 1 per cent. 

7. The loading should proceed gradually and uniformly, and not by 
sudden increments as by large pump-pulsations, or by the adding of over¬ 
weights by hand to the weighing-beam. The rate of loading should also be 
under perfect control. 

8. The machine should be so constructed as to permit the free use of 
appliances for measuring distortion of the specimen by some suitable device. 

9. If used for compression tests, one of the bearing-surfaces should be 
slightly adjustable to accommodate the machine to the non-parallel faces of 
the test-block, and these bearing-surfaces should be harder than any material 
tested by them. The neutral axis of these bearing-plates should coincide 
with the axis of symmetry of the applied forces as transmitted by the 
machine to the specimen. For these tests the machine should have a very 
slow movement. 

10. If used for cross-breaking tests, it should be furnished with means for 
measuring the deflection. To do this properly a rigid connection must be 


* This standard is given by the French Commission. 



MECHANICAL TESTS IN GENERAL. 


305 


established between the two end bearings to the middle bearing (or bear- 
ings), through parts not under stress , in order that the loading of the 
specimen may not disturb this rigid relation. 

11. Torsion testing-machines should apply the torsion movement as a 
true couple and without developing any tensile or bending stress in the 
specimen. 

12. Impact testing-machines should as far as possible satisfy the condi¬ 
tions imposed in Art. 292. That is, as far as possible, the entire energy of 
the blow should pass into the specimen. The falling weight should be held 
to its course either by vertical guides, in the case of a falling weight, or by 
a pendulum mounted on a transverse axis resting on knife-edge bearings. 
The former method is to be preferred. The falling weight should be sym¬ 
metrical in form, with suitable guiding attachments, to be formed (cast) in 
one piece, of hard metal, with its centre of gravity as low as possible. The 
height of the weight should be greater than the width between the guides, 
which latter should be quite rigid, true, and vertical, and should offer no 
frictional resistance to the falling weight. The supporting mass should be 
very great as compared to that of the falling weight. The French Commis¬ 
sion recommend that it be at least 15 or 20 times that of the striking body. 
Impact tests can only be standardized by using exactly similar appliances in 
all respects, including the supporting blocks and the foundation on which 
these supports rest. 

260. The Effect of the Rate of Loading on the Results of the Test. —The 

French Commission quote M. A. Le Chatelier on this subject as follows: 
“ Metals do not respond instantly to the deforming action of external forces. 
These deformations, both elastic and permanent, continue to increase with 
time, and the termination of the instant when the deformation correspond¬ 
ing to a given load has been fully completed depends only on the exactness 
of the measuring instruments employed. Speaking absolutely, this condition 
of equilibrium is never attained, and we may say the deformation increases 
indefinitely. It approaches, however, a limiting value (as an asymptote), 
especially in the case of elastic deformations, and even for permanent defor¬ 
mations the time may be found beyond which the remaining deformation 
will not exceed a given amount.” 

It is admitted, however, that for metals at ordinary temperatures a ten¬ 
sion test (for instance), extended over a few minutes’ time, gives practically 
the same results, in every respect, that would be obtained by any slower 
imposition of the load. This has been thoroughly established by Bauschin- 
ger, as well as by Considere and Le Chatelier. Zinc and tin are exceptions 
to this law, comparatively small external forces causing final rupture if these 
forces continue active. Copper and aluminum also fail under a somewhat 
smaller permanent load than is required to produce rupture in ordinary 
tests.* It is well known that timber yields continually under about one half 


* Report of the French Commission, vol. i. p. 93. 





306 


THE MATERIALS OF CONSTRUCTION. 


the breaking-load, and this half-load, permanently placed, may ultimately 
cause failure. For all kinds of test specimens of wrought iron and steel, and 
other structural metals, at ordinary temperatures, a test extending to one 
minute or more may he considered as giving normal results. 

For very rapid tests, or where rupture occurs in less than a minute, the 
breaking-load increases and so does the ultimate elongation. In the case of 
soft steel, however, which has a great local reduction of area, the elongation 
diminishes as the test period decreases, reaching a minimum for a period of 
about one minute, and then the elongation rapidly increases again for very 
quick tests, because it then reduces in cross-section more uniformly through¬ 
out its entire length. 

It has been shown by M. Considere * that the stress-diagram giving the 
simultaneous relation between stress and deformation is very different under 
very quick impositions of load, as in case of a shock, or impact, from the 
diagram for ordinary laboratory static tests of more than one minute dura¬ 
tion. His results are shown in Fig. 52, p. ?9. This subject is fully dis¬ 
cussed in Art. 292, where impact tests are described. 

In conclusion it may be said that in all ordinary tests of metals the test 
period should fall between one and six minutes. 

261. Significant Limits of Deformation. —Ever since the properties of 
building materials have been studied, “ the elastic limit ” has been defined 
both as the greatest load which will not produce a permanent set, and as the 
greatest load at which deformation remains proportional to the load, or 
stress. It has commonly been supposed that these two limits were one and 
the same, and in the commercial testing, which has probably been carried on 
in America to as great an extent as in any country, this so-called “ elastic 
limit” has been observed as the point at which the deformation increases 
rapidly under a constant load, or, as it has been called, the “ yield-point.” 
The French Commission has studied this subject with care, and after mature 
deliberation a majority have agreed to adopt three critical points, as follows: 

1. The elastic limit (“ la limite cVelasticity”), or the unit stress beyond 
which a portion of the deformation remains as a permanent set. (Point E 
of the stress-diagram.) 

2. The proportional elastic limit (la limite d } elasticity proportioned, or 
limite des deformationsproportionelles), corresponding to the point where the 
deformation ceases to be proportional to the loads. (Point P of the stress- 
diagram.) 

3. lhe apparent elastic limit (la limite dd elasticity apparente, or origine 
des deformations sons charge constante), corresponding to the point where the 
deformations increase rapidly without any increase in the force exerted. 
(Point F of the stress-diagram.) 

While in a scientific study of metals it may be important to determine all 
these three limits whenever they occur, in practical or commercial testing 


* French Commission Report, vol. n. p. 344. 




MECHANICAL TESTS IN GENERAL. 


307 


it will be found sufficient to observe the third one only, or the second only 
in case the third limit does not obtain for that material. The first of these 
limits has seldom been determined, since it involves a release of the stress 
by removing the load. This involves a great loss of time, since to determine 
this limit accurately the load would have to be released for each small incre¬ 
ment of, let us say, 1000 pounds per square inch for iron and steel. The 
second and third limits can be determined after the test has been completed, 
provided simultaneous readings of the load and deformation were taken 
during the test at frequent intervals, or provided an autographic stress- 
diagram was made by suitable attachments to the machine and test specimen. 
The third limit is commonly, but not accurately, determined in commercial 
testing in America, by “ the drop of the weighing-beam,” this marking the 
point where the deformation increases for very ductile metals under a con¬ 
stant load. 

With unrolled (or unforged) castings of the various metals any load pro¬ 
duces some appreciable permanent set, so that the first elastic limit does not 
•exist for such materials. It is probable that this is also true to an inappre- 



Fig. 247.—Average Curve of Four Tests of i-iu. Wrought-iron Rods. {Wat. Ars. 

Rep., 1888.) 


ciable degree of all the rolled metals, so that this is a very unreliable and 
unsatisfactory test of any important property of materials. The law of 
proportionality is much better defined, but, owing to the mixed character of 
the elementary forms entering into the composition of all metal products, 
even the purest, this law is often found to fail when the most refined means 
of measurement are employed, since there then seems to be no strictly con¬ 
stant ratio between the load-increments and the corresponding increments 
of the deformation, and hence the exact point where this ratio begins to 














































308 


THE MATERIALS OF CONSTRUCTION. 


change is in these cases difficult to fix. In such cases, by plotting the 
deformation to a very large scale with the loads, one can determine graphi¬ 
cally, as in Fig. 247, about where the deformation increments begin to 
increase. The second and third elastic limits are marked on this diagram 
“true elastic limit” and “yield-point” respectively. The “apparent 
elastic limit,” or “ yield-point,” is the most important and significant of the 
three, as well as the most easily determined, but in high carbon-steel, 
especially in hard-steel wire and in all cast metals, and often in wrought 
iron, this point does not appear, in which case the “ proportional elastic 
limit” takes its place, as shown in Fig. 249, where it is marked as the 



Fig. 248. —Typical Stress-diagram of Hard-drawn Brass. ( Wat. Hrs. Rep., 1886.) 
“ U. S. Elastic Limit” is that given in the published report.) 


(The 


“ true elastic limit.” Sometimes, also, when point A 7 is very marked, point 
P is found above it, as in Figs. 7 and 8, pp. 15 and 16. 

262. All these Absolute Elastic Limits Unsatisfactory. —It is proposed 
now to show that no one of the three definitions of elastic limit given in 
Art. 261 can be used in practice. They all will be shown to be either abso¬ 
lutely indeterminate or Avholly dependent on the delicacy of the measuring 
apparatus, rather than on the qualities of the material tested. 

Thus the first two definitions undertake to fix a limit , and evidently the 
position of this limit is simply the point where either the permanent set or 
the deviation from a linear relation between load and deformation becomes 
measurable. If one can measure accurately to 0.0001 inch, he will discover 
these limits earlier, or at a lower stress, than if he can only measure to 0.001 
inch. The French Commission recommend that measurements be made to 


































MECHANICAL TESTS IN GENERAL. 


309 


the nearest 0.001 mm. or to j'sion inch* To discover a permanent set, 
furthermore, requires a constant release of the load, which is liable to disturb 
the deformation-measuring apparatus, and in any case the load at which a 
permanent set occurs can only be said to lie between two particular loads, 
the greater of which has produced the first permanent set observed*. The 
time and trouble involved in releasing the load so often will act to remove 
this test from nearly all scientific and commercial work. 

It has generally been assumed that the first two definitions of elastic 
limit given in Art. 2G1 locate identical points in the stress-diagram, but 



Fig. 249.—Tension Tests of Steel Piano-wire. Gauged length 6 in., Diam. 0.04 in. 

( Wat. Ars. Rep., 1894.) 

with the most delicate measuring appliances it is found that these two defi¬ 
nitions may locate points very far apart. 

The third definition is also indefinite, since it remains a question as to 
which load is to be taken, the higher load at which the first great permanent 
elongation occurred, or the lower load under which this elongation continues 
to spread throughout the entire length of the bar. These often differ as 
much as from 3000 to G000 pounds per square inch. (See Figs. 7 and 8.) 

Again, when the most delicate apparatus is employed, several specimens 
from the same bar of the most uniform material may give elastic limits of 
either of the first two kinds which differ widely from each other and hence 
become mutually contradictory. In other words, such delicate tests are quite 
worthless for all practical purposes, i.e., the results are not characteristic. 

263. The Apparent Elastic Limit. —The term “ relative elastic limit ” 
was coined by the author in 1891, to be used in his work of testing timber 
for the Forestry Division of the U. S. Agricultural Department. lie then 























































310 


TEE MATERIALS OF CONSTRUCTION\ 


defined it as the point on the stress-diagram (of tests in cross-bending) 
where the rate of deformation is fifty per cent greater than it is at the origin 
(see Figs. 247, 248, and 249). To find it draw a tangent to the stress-diagram 
at the origin, and then lay a parallel ruler on a line making with the load 
line an angle whose tangent is fifty per cent greater than that of the original 
tangent line, and then move the ruler until its edge becomes tangent to the 
stress-diagram, and draw such tangent line. The “ relative elastic limit” 
is then located by eye as this ]ooint of tangency. In the tests of wooden 
beams this point usually falls on the diagram where its curvature is about 
the most rapid (radius of curvature a minimum), and in all tension stress- 
diagrams of the various metals it will he found to marl a well-defined point, 
whose coordinates are practically fixed and constant for the same material. 
While this point is certainly beyond all “ true elastic limits” when defined 
as limits , yet in the metals it will he found to fall very little beyond such true 
limits. In fact it commonly falls below the “ elastic limit ” recorded in all 
the Watertown Arsenal Tests, where the deformations were measured and 
recorded to the nearest y-frVro au inch, as shown in Figs. 9 and 248, 
and many others in Chapter XXIV. 

The French Commission make use of the term “apparent elastic limit ” 
to indicate what in England is called the “ yield-point ” or “ break-down 
point,” and in Germany is called the “ beginning of great elongations.” 
But with such materials as cast iron, high carbon-steel, and often with 
wrought iron and other metals there is no “ yield-point,” or no point where 
the material deforms under a constant load, unless it he at the point of 
maximum load, to which of course it is not intended to apply. The term 
“ apparent elastic limit ” in this sense, therefore, has not a universal appli¬ 
cation, and hence cannot be used as the commercial elastic limit to he em¬ 
ployed in practical tests. 

The term “ apparent elastic limit ” has not as yet come into use in 
English; and if it now he defined arbitrarily as the term “ relative elastic 
limit ” is defined above, it could have this specific meaning and would he of 

universal applicat io n. 

When so located it will be found at practically the same point on all tests 
of like kind on similar materials. It is therefore characteristic of the 
material. 

It does not require the use of expensive and troublesome appliances for 
its accurate location. Relatively crude appliances can be used to measure 
the deformations; and though these may not fall on a smooth curve, a mean 
line drawn through them, as the stress-diagram, furnishes a satisfactory 
means of locating this “ apparent elastic limit. ” It is therefore a practically 
determ inate f unction. 

It can readily be determined from an automatically registered stress- 
diagram, of any description, thus admitting of a continuous and uninter¬ 
rupted progress of loading, so that the conditions of a test can be exactly 
duplicated as to speed, which cannot be done when the test is stopped to 



MECHANICAL TESTS IN GENERAL. 


311 


take deformation readings. It is therefore a true relative limit of the elastic 
field. 

Although this point is slightly beyond the true elastic limit, it will mark 
a point corresponding to a permanent set much less than can be measured on 
any scale by the naked eye,* and hence it may be regarded as the trice elastic 
limit for commercial purposes. 

It serves perfectly to classify materials as to the maximum loads they can 
resist without receiving deformation which would injure them for continued 
sendee, these being the real “ultimate loads” for all practical purposes. 
It marks, therefore, the most valuable and important property of all engineer¬ 
ing or building material. In other words, it is the most essential character¬ 
istic point on the stress-diagram. 

In the opinion of the author of this work, therefore, an “ apparent elastic 
limit,” defined and determined as here described, is the best if not the only 
satisfactory solution of this troublesome question. The fifty per cent increase 
in the rate of deformation was chosen as being about the least which would 
mark a well-defined point of tangency on the stress-diagram. Since it 
always marks a point which corresponds to an extremely small permanent 
set, there would seem to be no objection to its use. 

* Seldom more tliau one one-thousandth of one per cent of the measured length. It 
is a maximum in the case of the high-grade, hardened steel wire, shown in Fig. 249, 
where it reaches about -fo of one per cent. See Engr. News , vol. xxxiv. p. 56 (July 25, 
1S95) for a discussion of Elastic Limit, in which an arbitrary rate of deformation two or 
three times that inside the true elastic limit is recommended as that marking the com¬ 
mercial or practical elastic limit. 








CHAPTER XV. 


TENSION TESTS. 

264. Significance of Tension Tests.—Tension tests are at once more com¬ 
mon, more readily made, and more useful in revealing the true character of 
a metal than any other kind of mechanical test. In fact, when other kinds 
of tests are made it would commonly be well to accompany them with a few 
tensile tests for the purpose of being able better to coordinate the results 
with those obtained on other materials by similar tests, or on like materials 
by different tests. In this connection, however, it is w T ell to remember that 
all the metals are wanting in strict homogeneity, and that they may be 
regarded as aggregations of more or less dissimilar elements embedded in a 
common matrix, somewhat like granite. (See Arts. 105 and 108.) For 
instance, the planes of rupture will be different for different kinds of tests 
on the same specimen, and hence the strength developed will be that of a 
different combination of elements in each case. Also, the strength to resist 
various kinds of stress may lie in entirely different elements of the aggrega¬ 
tion, as, for instance, in the case of cast iron the strength to resist tension is 
the strength of the graphitip carbon matrix in which the iron crystals are 
embedded, while the strength in compression is largely the strength of the 
iron crystals themselves.* 

What we call the maximum strength of the material, therefore, or its 
strength at rupture, is not usually the sum of the maximum resistances of the 
several elementary portions of the cross-section, since they do not all distort 
equally. It is often the case that actual rupture occurs successively over 
many elementary portions of the broken section before the final failure 
occurs. More especially is this true of the elastic limits of the material, 
while with iron and steel castings this failure in detail is so prominent as to 
cause the'stress-diagram to be a curve almost from the beginning of the load¬ 
ing. Here, too, the irregular shrinkage often leaves very great internal 
stresses in the body, which causes some portions to come to their elastic 
limits and ultimate strength much earlier than others, again giving rise to a 
curved stress-diagram. 

For these reasons we find, when the most delicate means are employed to 
measure deformations under increasing loads, that in almost no case is the 


* M. Osmoud. 


312 




TENSION TESTS. 


313 


deformation strictly proportional to the load, and that even very small loads 
will produce some little permanent deformation or set. This is why the 
definitions given in Art. 261 must depend on certain arbitrary limits of 
deformation and set, and are not true absolutely as they have hitherto 
commonly been defined. 

The tension test is especially well calculated to show what local irregulari¬ 
ties may be found in a finished product, and to indicate to what extent the 
work of forging (rolling or hammering) has produced that degree of hoino- 
genity expected of it. 

The tension test is more readily standardized than any other so as to be 
independent of “ personal equation ” and of variations in the testing-machines 
employed. It also demands the least amount of preparation of the test 
specimen, if tests are to be made only for commercial purposes. Except for 
the inherent want of uniformity or of homogeneity mentioned above, there¬ 
fore, the tension test may be made to give typical and uniform results, and it 
should be considered as the best single test to make on any of the metals. 

265. Selection of the Test Specimens.—Test specimens may be taken 
either from the finished product or from the material when poured if it is 
derived from a fluid condition. In American steel mills it is common to 
roll (or hammer) a test rod from a small ingot poured from each heat, 
whether it be of the Bessemer or the open-hearth process, and the maker 
depends on the tests made on this bar to guide him in the further use of the 
ingots poured from that heat. The user also is often satisfied with these 
tests, especially when his requirements are not very rigid. 

In making iron and steel castings it is common to have test samples 
cast in the same moulds with important castings, and joined thereto, so that 
they shall represent, of necessity, the identical metal of which the structural 
form is composed. If special moulds are used for these test specimens, they 
should be of dry sand, under a head of at least eight inches, and with an 
inclination of at least one in five to allow the escape of the gases. With 
very heavy castings (over three inches in thickness) test specimens may be 
cut from the head itself which is cut off from the upper end of the casting. 

If the specimens are taken from rolled structural forms, they should be 
taken from the thicker parts, which have received the least work in the 
rolls. The thinner parts are always harder, have higher elastic limits and 
greater ultimate strength. 

With wrought iron a great difference will be found in specimens cut with 
and across the direction of the rolling, the former having much higher 
strength and a greater ductility. . In steel plates there is little difference, 
and in rolled brass and copper plates there is no difference. In the case of 
the bronzes it is necessary to have test samples poured from different parts of 
the same melting, as the mixture changes its characteristics rapidly when in 

a melted state. 

266. The Preparation of the Test Specimen.—In order that the test 
specimen may fairly represent the material under examination, or the par- 


314 


TEE MATERIALS OF CONSTRUCTION. 


ticular jfiate, or bar, or rolled form from which it is to he taken, it is neces¬ 
sary to observe a number of rigid requirements. 

The specimen must be obtained by cutting it out in a way that will leave 
it perfectly straight. If it is bent in getting it out, it should be heated to 
straighten it; but this may often change the original molecular arrangement, 
and should be avoided if possible. When the specimen is cut from a larger 
portion of a plate or rolled form by shearing, it will invariably take a curved 
form. In this case the plate , or form , should be sheared away from the 
specimen , in narrow slices, so as to leave the test specimen unbent. If the 
specimen is bent and then straightened, it raises the elastic limit and hardens; 
the metal, the same as any other kind of cold working. Instead of shearing, 
some milder process, such as planing or drilling or sawing, should be resorted 
to to obtain the test specimen. For, besides the bending action on the bar 
as a whole, the effect of the shearing or punching is to seriously injure the 
metal for about an eighth of an inch beyond the sheared surface, leaving it. 
so non-ductile, or brittle, that it will not elongate appreciably, and hence 
under a tensile test these surfaces will be severed very early in the test, and 
the cracks so started may cause the remainder of the cross-section to tear 
asunder in detail. To prevent this action on sheared or punched specimens, 
at least an eighth of an inch of thickness should be removed from all 
punched or sheared faces, by reaming, planing, or filing. The effect of not. 
doing this is shown in various figures in Chapter XXVI, where both punched 
and drilled test specimens of one-fourth inch iron and steel plates had been 
grooved for testing, leaving varying widths of metal between the bottoms, 
of the grooves. The effect of this variation in width is also here shown. 
Various bending tests there shown also exhibit the weakness resulting from 
shearing and punching. 

The ordinary lathe, planer, and milling-machine tools are not suitable 
for the final finishing of the specimen, as they tear and bruise the remaining 
metal, giving rise to a condition favorable to the starting of incipient 
fractures at the surface of the specimen. These tools may be used for 
roughing out the shape desired, but it should be finished with the file, and 
in case of the softer metals, like copper, the file should be followed with fine 
emery-paper. 

Castings should be cut down about an eighth or a tenth of an inch from 
the rough exterior, on the reduced section, and they should also be trued-up 
on the ends which are to be gripped.* Rectangular edges should always be 
taken off by a file to remove any incipient cracks or irregularities which may 
be left here by a kind of crushing-down action of the tools operating on one 
or both of the plane faces meeting on these lines. Test specimens of the 
softer metals should never be beaten with a steel hammer, but with wooden, 
or copper mallets, if it is necessary to use such means to straighten them. 

Standard shapes of test specimens are shown in Fig. 251. 

* For commercial purposes a cheap form of specimen which is tested without turn¬ 
ing down at all is shown in Chapter XXIV. 







TENSION TESTS. 


315 


RULES OF THE FRENCH COMMISSION FOR TENSION TESTS. 

1. The test should be continuously progressive. 

2. The duration of the test should in a general way increase with the volume 
of the specimen. 

3. For standard tests on specimens of ordinary dimensions of which the sectional 
area is not more than one square inch (600 sq. mm.) and the measured length not 
more than eight inches (20 cm.) it seems that the duration of the test should be 
included between one and six minutes. 

4. For test specimens having a thickness less than 0.2 in. (5 mm.) the duration 
of the test should be less than thirty seconds. 

5. It is necessary to avoid, especially with soft metals, producing a sensible 
heating of the test bars. 

267. Standard Dimensions of Tension-test Specimens. — It has been 
shown* that so long as the test specimens of a given material maintain the 



Fig. 250. —Showing the Constancy of the Strength and of the Elongation when 

. ^ = a constant (8 in this case). Each result is the mean of five tests on the same 
VA 

material. ( French Com. Hep., 1894, vol. in. p. <2.) _ 

* By MM. Lebasteur, Marie, and Barba. See Hep. French Commission, vol. m. 
. 23. * 


































316 


THE MATERIALS OF CONSTRUCTION. 


same relative dimensions, or are geometrically similar in form, the strength 
and the percentage of elongation remain constant, as shown in Fig. 250. 
The French Commission have, therefore, adopted the relation T = 66.67.4, 
or for cylindrical specimens l — 7.2c/, where l is the measured length on 
which percentage of elongation is computed. An eight-inch specimen would 
then be 1.11 inch in diameter, or nearly 1 sq. in. in area of cross-section. 
Since this relation between l and A was chosen for convenience (for / = 200 
mm., A — 600 sq. mm.), persons using inch units might well choose the 
relation / = 8c/, or 

V = 81 A .(1) 

For square sections, therefore, 

l = 95,.(2) 

while for round sections 

l=8d ,.( 3 ) 

these being intermediate between the French and the German standard 
dimensions. * 

Equations (1), (2), and (3), therefore, may be employed in finding what 
length of specimen to use to give comparable and consistent percentages of 
elongation, when the excessive elongation near the broken section is included. 

If it is practicable to so prepare the specimen as to make the area of the 
cross-section nearly constant, then a fixed length of specimen could be used 
for all tests. Thus for the standard length of eight inches the diameter of 
round specimens would be one inch. Where the cross-section varies from 
this the lengths should vary in accordance with equation (3). Thus 


For diameters of 

l 

inch 

make / = 

i 

inches, 

a 

( 

C c 

f 

< ( 

4 4 

l = 

6 

4 ( 

a 

( ( 

< i 

5 

8 

(( 

(i 

l = 

5 

ii 

( i 

C i 

i i 

1 

(( 

L i 

/ = 

4 


(< 

( ( 

11 

3 

8 

t i 

i ( 

/ = 

CO 

( ( 

i 6 

i i 

<( 

1 

4 

t i 

t ( 

/ = 

2 

< ( 

i i 

a 

i i 

1 

8 

i ( 

t ( 

/ = 

1 

( < 


For plate tests we have, from (2), 

1‘ — 81 A = 815/, or 1 = 9 VU .(4) 

Since'it is common to prepare several of these together in a milling- 
machine, it is desirable to have a common width for these tests, and a width 
of one inch has been usually employed in America. This may be done if 
the lengths are varied to give comparable results. Thus, from eq. (4), 
/ — 9 Vbt, the following scheme of lengths and thicknesses is derived, the 
width being one inch in all cases: 

* The German Commissions have agreed on l— 11.3 X A = 10 d for round section 
and 11.36 for square sections. 







TENSION TESTS. 


317 


For plates J inch thick 

make 

rH|(N 

II 

inches. 

(( 

u 

2, 

8 

cc 

(( 

<( 

1= 5i 


(( 

a 

i 

a 

a 

a 

1= 6J 

<< 

a 

(< 

| 

(< 

a 

(( 

II 

u 

« 

u 

1 

a 

« 

(< 

II 

iNm 

a 

u 

a 

i 

u 

(< 

<( 

l — 8-2- 

t i 


For thin sheet metal make the measured length always four inches, and 
use three standard widths as follows: 


For thicknesses from 0.1 inch to 0.2 inch make width = inch. 

a 0.05 “ “ 0.1. “ “ " = f “ 

“ “ less than 0.05 inch “ “ = \ “ 

All these relative dimensions agree closely with those recommended by 
the French Commission (1895). 

The measured portion of the reduced section (called l in the above 
discussion) must be removed from the shoulders by a distance at least as 


-47)— 


T 

B 




r.=X in. 




T~ 

b 


~F 

b 


Jee. 


-47)- 


£Ubt — 


in. 







Fig. 251. —Standard Dimensions for Rectangular and Cylindrical Test Specimens. 


great as the diameter or thickness of the test bar, in order to avoid the effect 
of these enlarged portions in reducing the elongation. The reduction of the 
percentage of elongation near the ends is well shown in Fig. 252, where the 
bar had a total reduced length of 15 inches and a diameter of 1-^- inches. 
Steel bars of this shape will break near the centre, while wrought-iron bars 
will break at various distances from the centre, with a more uniform distri¬ 
bution of the elongation. 


268. Tetmajer's Analysis of the Elongation of Tension-test Specimens.*— 

The typical forms of tension-test specimens are shown in Fig. 251, where both round 
and rectangular sections are given. It has been shown by numerous experiments 
that the strength and the reduction of area are somewhat dependent on the form of 
the test specimen, while the elongation is very greatly dependent on these relative 
dimensions. This is well illustrated in the reproduced photographs shown in 
Fig. 10, and also in the elongation-diagrams Figs. 252 and 253. Here are shown first 
the original specimens, then the specimen stretched to its maximum loading, the 
elongation being nearly uniformly distributed over the length, and finally the speci¬ 
men greatly reduced at one point where rupture is about to occur. It is evident, 


* Tetmajer’s Communications, vol. iv. 






















































318 


THE MATERIALS OF CONSTRUCTION. 



Fig. 252.—Showing Distribution of the Elongation over a Steel Bar 15 in. Long and 

2 in. in Diameter. (Rep. Fr. Com., vol. in, PI. ii.) 



Fig. 253.— Showing the Variation in the Distribution of the Elongation of the Several 
Inch-spaces of Six-inch Test Bars of Steel and Wrought Iron 0.56 in. in Diameter. 
(Wat. Ars. Rep.. 1890.) 















































































































































































































































































TENSION TESTS. 


319 


from a study of these specimens, that the total elongation of tension-test specimen 
may be divided into two distinct parts, namely: 

1. The general elongation. 

2. The local elongation. 

It will further appear that the local elongation is nearly the same in all cases, 
and is practically independent of the length, while the general elongation, having 
occurred uniformly along the bar, is directly proportional to the length. 

If l = measured length of specimen, 

Jl = total elongation, 

A = proportional distributed elongation 
distributed elongation 

i : > 

Al 0 = total local elongation 

then /l may be found for any given test by measuring Al for two lengths of the 
same specimen, each to include the broken section. Since the standard length 
of specimen is 8 inches (200 mm.), it usually will be found convenient to use 8 
inches and 4 inches for these two lengths. If the specimen be marked originally 
every inch, then after it has broken two sets of these marks may be chosen, each 
pair to include the fracture, and to be points originally 8 inches and 4 inches apart 
respectively. Then we may have 

Ah = 8A + Ah 
Al, = 4A + Ah 

Ah — Mk — 4A 
or 

A — K^h — Ah) .(1) 

This function, A, obtained in this way , is independent of the length of the speci¬ 
men, and is the true characteristic elongation of the material. 

It would seem that this function is the one to be generally adopted as the true 


index of the ductility of the material. Unfortunately custom has established —- as. 



Fig. 254.—Elongation of a Specimen of Copper 200 mm. Long for the Loads as given. 

(Fr. Com. Rep., vol. in. PI. vn.) 


the ductility function, or “the percentage of elongation,” and this varies greatly 
with the ratio of length to form and area of cross-section. 

Professor Tetmajer shows that the following relative dimensions give practically 
equal percentages of total elongation: 


(a) cylindrical specimens. 


Diameters. . 

0.4 in. 

0.G in. 

0.8 in. 

1.0 iu. 

Observed length. 

4.0 in. 

6.4 in. 

8.0 in. 

10.0 in. 

Mean observed elongation, “ Phoenix” steel... 

30.1# 

30.4# 

30.5# 

30.6# 
















































320 


TEE MATERIALS OF CONSTRUCTION. 


(b) rectangular specimens, ALL 0.4 IN. THICK. 


-r, . b 

Ratio : - = 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

4.0 

4.5 

Observed length, inches.. 

4.0 

4.8 

6.0 

7.2 

8.0 

8.0 

8.0 

8.4 

Mean observed percentage 
of elongation. 

27.0 

27.2 

27.2 

26.8 

26.1 

25.7 

26.1 

26.7 



Each of the above observed elongations in Table (A) is the mean of five tests and 
in Table (B) of ten tests, and the results indicate that equivalent lengths were used. 
When the length was taken as 8 inches in each case, the percentage of elonga¬ 
tion in Table (A) ranged from 26.5 to 32.4, while in Table (B) it ranged from 21.3 
to 28.6. These results are consistent with the rules laid down by the French Com¬ 
mission and which the author has interpreted approximately in English measures in 
the previous article. 


269. The Time Function of Tension Tests is not an important one. 
Bauschinger has shown that within the ranges of practicability the time 
element is of no consequence. This is also shown in Fig. 255, where results 


78000 


60,000 


50000 


40.000 


30,000 




560/. 

OT/OA 

/ 








(//TO, 

P 

—-< 

-- 

>- 


-< 























t liJ/ 

T 




A 


lL 

4 ST/0 

Ltw 




§ 

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Eig. 255.—Showing the Effect of Pulling Speed of the Testing-machine on the Recorded 
Results with Structural Steel. (Campbell's Structural Steel, p. 253.) 


obtained with the greatest rapidity obtainable in the American standard 
testing-machines are compared with results from very slow tests, with very 
little difference in the results. The greatest recorded differences are found 
in the elastic limit; but as these were all observed by the “drop of the 
beam,” it is likely that the speed had more to do with the obtaining of the 
reading than it had with the real action of the material itself. 

270. Tension-test Machines. —There are three general types of universal 
(tension, compression, and cross-bending) testing-machines on the American 
market, viz., hydraulic machines, screw-gear machines, and the Emery 
machines. The hydraulic-power machines have, however, been practically 
abandoned in favor of the screw-gear for all experimental and commercial 





































































TENSION TESTS. 


321 


purposes, while for high scientific accuracy and an incredible delicacy 
nothing ever made can compare with the Emery machines.* The first two 
varieties of machine owe their present high state of development largely to 
Mr. Tinius Olsen, and the Emery machine was originally designed by Mr. 



A. II. Emery, but has since been greatly simplified and improved by Wm. 
Sellers & Co., the present manufacturers. 

The hydraulic machines have some advantages when operated by hand, 
but they all have the disadvantage that it is impossible to maintain a given 


* The hydraulic and screw-gear machines are made by Tinius Olsen and by Rielile 
Bros., and the Emery machines by Wm. Sellers & Co., all of Philadelphia, Pa. 



























































































































322 


TEE MATERIALS OF CONSTRUCTION, 


load without continuous pumping to supply the small leakage which always 
occurs. 

The Olsen screw-gear 100,000-lb. testing-machine, shown in Fig. 256, 
will be taken as a type of the testing-machines which are almost exclusively 
employed in America. The power is applied to the pulleys 26 and 27, the 
former used for direct (downward) and the latter for reverse (upward) 
motion of the moving cross-head, 5. Extremely slow speed is obtained by 
throwing into contact the small friction-gear 35, operating upon the large 
wheel 34, which is rigidly attached to the driving-shaft. This is effected by 
drawing on the chain 37 by turning the hand-wheel 39, which tightens the 
band 42 and starts 35 to revolving. The band-wheels 26, 27, and 43 all 
revolve freely on the driving-shaft, except as 26 or 27 is made fast to it by 
the friction-clutch 28, 30, through the hand-lever 33. 

A medium speed of the moving cross-head is obtained by simply throwing 
26 in gear by the hand-lever 33, and a high (upward or downward) speed is 
attained by changing the gears by means of lever 25, the upward speed 
greatly exceeding the downward because of the different band connections 
on the direct and on the reversing-pulleys 26 and 27 respectively. 

The moving cross-head, 5, is brought down by the turning of four screws, 
one at each corner, only two of which are visible in Fig. 256. A tension- 
test specimen is placed between this moving head-piece and the fixed cross¬ 
head above, being gripped in each by means of hardened steel wedges with 
grooved faces. The pull on the specimen is thus transmitted through the 
four cast-iron columns, 2, to the weighing-table, 3, which rests by means of 
fixed spurs upon the three weighing-levers, 117. Between these and the 
weighing-beam, 118, there is one intermediate multiplying-lever (not num¬ 
bered). The large poise, 106, in this machine is supposed to be moved by 
means of the screw 105, which is under automatic electric control. When 
the beam lifts, the screw is put in motion; and when it leaves its upper con¬ 
tact the screw stops its motion. The weighing-beam is thus automatically 
maintained in constant balance. If operated by hand, the large poise, 106, 
is set forward by full revolutions of the screw by means of the handle shown, 
and the intermediate loads indicated by balancing with the small poise shown 
at the right-hand end of its scale, 118'. When operated automatically this 
poise is not used, and the fractional part of the total load is read on a grad¬ 
uated disk attached to the screw at the left-hand end, but not clearly shown 
in the figure. 

Compression tests are made by attaching a compression-block to the lower 
side of the moving cross-head, and inserting the specimen between it and the 
weighing-table, 3. 

Cross-breaking tests are made by jilacing the end bearings on the weigh¬ 
ing-table (or on an I-beam resting on this table if the specimen is long), and 
attaching a knife-edge bearing to the lower side of the moving cross-head. 

A machine in nearly all respects quite similar to the above is that shown 
in Fig. 257, made by Iliehle Bros. The poise here is moved by a chain 


TENSION TESTS. 


323 


passing over a driving-pulley, which pnlley is operated either by hand or by 
power under electrical control, the same as the screw in the Olsen machine. 
Only two screws are here used for moving the pulling cross-head, instead of 
four as in the former case. Both forms of machines are made in the highest 
style of the art, both being the survival of the fittest in a long succession of 
types of testing-machines. They are by far the most useful and convenient 
testing-machines made,* and are not likely to undergo much change in the 



Fig. 257. 

future. (They are now, 1896, being sold in Europe.) The speeds at which 
the machine shown in Fig. 257 may be driven directly are as follows: T V in. 
per min.; £ in. per min.; f in. per min.; 1-^- in. per min.; and 8 in. per min. 
For tests of low ultimate strength, speeds of in. per min. and of 4 in. per 
min. can also be used. The higher speeds, down to f in. per min., can also 
be used in raising the moving head. By changing the speed of the main 
shaft from which power is obtained all these speeds can be increased or 
diminished at pleasure. The speeds as given above are for 150 revolutions 
per minute of the driving-pulleys on the testing-machine. 

In Fig. 258 is shown a small screw-gear power machine, made by Biehle 

* The author offers no apology for not giving descriptions of any of the scores of 
styles of machines which have been built and which are still in use—mostly in Europe. 
They will never be built, bought, or used in this country, and most of them can be 
found illustrated in the Report of the French Commission. 1895, vols. n. and in. 












































































































































(rtTV I 


324 


THE MATERIALS OF CONSTRUCTION. 


Bros, in capacities of 20,000 lbs., 30,000 lbs., 40,000 lbs., 50,000 lbs., and 
60,000 lbs., with hand-power attachments, and automatic weighing appli¬ 
ances if desired. With the 20,000-lb. machine the hand-power does very 
well,* although steam or electric power is always preferable. Autographic 



Fig. 258. 


recording attachments (see Art. 275) are attached to these the same as with 
the larger machines. They are too small, however, for general commercial 
purposes. 

271. Gripping Devices. —A great variety of gripping devices have been 
employed, such as eyes and pins, shoulders and split-sleeves, screw-threads 
and nuts, and plain bars with wedge-grips. This last form has now replaced 
all others in America except such as may still be employed on some of the 
older machines. For round specimens notched grips are used, while with 
square or flat specimens the plain wedges are employed. The Riehle plain 
grips are swelled in the centre so as to grip the specimen hardest along its 

* These small machines are the best patterns for students’ use. It is better to have 
several of these than one larger machine. They serve almost every purpose in a course 
of study on the strength of materials. 




























































TENSION TESTS . 


325 



Fig. 259 



























































































































326 


TEE MATERIALS OF CONSTRUCTION. 


axis of symmetry. The Olsen grips are swivelled on spherical bearings at 
the back to enable them to more readily adjust themselves to the specimen. 





1IM 





Waj;. III!] Ml 

11 fflBIslw' 

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00 TO *0 SO 00 7 0 80 80 lOO no WO '«■ ||||i1 

--- T -- ■-r- - -r ■ - r r ' 1 r— r .jjjfc 

0 1*0 iTt 'to <»« K3 no tn rir> mo no *00 »7« >10 r*o »eo 000 jclllM'' 


III 

\J /Mm 


Fig. 260. 

The wedge-grips can be used with plain bars and plates, without any reduc¬ 
tion of section, as well as with specimens specially prepared by turning down 
or by a milling-machine. 


























































































































































































































































TENSION TESTS. 


327 


272. Similar Machines for Various Special Purposes. —In Fig. 259 is 

shown an Olsen machine designed for testing full-sized structural specimens, 
whether tension or compression members, or beams, and made in capacities 
of 200,000, 300,000, and 400,000 lbs. These machines have all the rates of 
motion, and the automatic weighing and autographic recording appliances 
described with the smaller machines. The height may be made almost any¬ 
thing which may be desired. 

In Fig. 260 is shown a similar machine of 300,000 lbs. capacity, in which 
the four cast-iron corner-posts are replaced by two large compression-screws. 

Fig. 261 illustrates a convenient and cheap machine for testing hoop-iron 



Fig. 261. 


and round bars, in tension only, of 20,000 lbs. capacity, suitable for office 
use.* 

In Fig. 262 is shown one form of a wire-testing machine , made by Olsen, 
in capacities of 10,000, 15,000, and 20,000 lbs. It is also adapted for test¬ 
ing band-iron and other forms, and could also be used for compression and 
cross-breaking. (iSee also other wire-testing machines in Chap. XXXIII.) 

Fig. 263 shows a form of cloth- and paper-testing machine,! having a 


* Made by Rielde. 
f Made by both Olsen and Riehle. 














































328 


THE MATERIALS OF CONSTRUCTION. 


capacity of 200 lbs. on one inch in width of material, while Fig. 264 shows 
another form, for paper only, of 100 lbs. capacity. The stress is indicated 
on the face of the dial. 

Tension-testing machines for breaking cement briquettes are shown 
and described in Art. 324. 

273. The Emery Testing-machine. —This is without doubt by far the 
most perfect weighing-machine ever devised. It was originally invented 



and constructed by Mr. A. H. Emery, C.E., for the use of the U. S. Test 
Board in 1879, and this first machine, having a capacity of 800,000 lbs. 
in both tension and compression, is still in daily use at the IT. S. Arsenal 















































































































































































































TENSION TESTS. 


329 



now manufactured in various sizes by Wm. 
Sellers & Co. of Philadelphia, who have modi¬ 
fied and improved the original plans in many 
respects. It is not too much to say of this ma¬ 
chine that it operates absolutely without fric¬ 
tional resistance, tests with equal accuracy large 
and small specimens, is easily and quickly 
operated, and is practically indestructible by 
any amount of legitimate use. The marvellous 
character of this machine merits a careful study 



Fig. 263. 


Fig. 264. 


by all students in engineering, and an attempt is here made to adequately 
describe it.* 

The essential principle of this machine consists in a means of transmit¬ 
ting a definite percentage of the force applied to the specimen to the scale- 
beams, and there weighing it accurately, without any friction whatever in 
the receiving, transmitting, or weighing parts. Hence any very small 
increment of the force applied is weighed with equal accuracy, whether this 
increment is added to a great or to a small previous load.f This is accom- 


* The author has been greatly aided in this by drawings and descriptions made by 
Mr. Carl G. Barth, M.E., who is one of the joint inventors and patentees of the various 
improvements made on it by Wm. Sellers & Co. 

f When the first machine was tested, a steel bar, 5 in. in diameter, was first broken 
under a load of 722,800 lbs., aud then a single horse-hair was tested, and the machine 
gave the strength (16 oz.) of this as accurately as a small spring-balance which was used 
for a check. Rep. U. S. Test Board , vol. n. p. 1. 

























































330 


TEE MATERIALS OF CONSTRUCTION. 


plished by means of two connected metallic sacks, or bags, of different sizes,, 
the larger one, called the hydraulic support , receiving the full force trans¬ 
mitted through the specimen, while the other is rigidly held upon the 



primary weighing-beam. Thus in Fig. 265, which is merely a schematic 
drawing, the load is received on the hydraulic support shown at A , and the 
pressure is transmitted by means of the enclosed liquid through the pipe e 
to the smaller sack at B , which being rigidly supported by the heavy cast- 
iron frame, 6r, shown in section above and below, the bearing-plate c is. 
forced downward, causing the block H to press upon the primary lever C * 



























































































































































































































































































































































TENSION TESTS. 


331 


This is then transmitted through D to the weighing-beam E and the indi¬ 
cator-arm F. 

In place of knife-edges on the weighing-beams, thin plates of steel are 
employed, these being rigidly fastened in the two attached beams. These 
are so proportioned as to bring the combined bending and compression 
stresses produced in them well within their elastic limits. While these offer 
absolutely no friction, they do offer some elastic resistance, but this is all 
allowed for in calibrating or standardizing the machines. The weighing- 
beam is kept in balance by lowering upon it various weights which are placed 
upon the several poise-frames which are suspended from this weighing-beam. 
The particular manner of doing this, though ingenious and peculiar to this 
machine, is not essential and will not be further described here.* This part 
of the apparatus is entirely closed by a glass front, and it is never necessary 
to open it, the weights being imposed and removed from outside, and the 
load continuously indicated on a counter-cylinder shown in Fig. 265 at the 
left end of the indicator-arm F. 

Passing now to a study of the latest form of the machine itself and its 
essential details, we have in Fig. 266 a view of the 200,000-lb. testing- 
machine made for Sibley College of Cornell University. To the left is seen 
the fixed weighing-head , containing the hydraulic support, and to the right 
the movable straining-head ,f or hydraulic cylinder, by means of which the 
load is applied to the specimen and its deformation taken up. Both of these 
are supported and kept in alignment on a substantial wrought-iron girder- 
bed. In the background is also clearly seen the wooden case containing the 
scale, with some of the levers and poise-frames visible through its glass front, 
and also part of the hydraulic pump which supplies the straining-cylinder at 
either end, according as the machine is being used for a tension or a com¬ 
pression test. The supply- and exhaust-pipes are seen coming up through 
the floor at the end of the bed, and connecting with the straining-head by 
means of jointed pipes as shown. Rigidly secured to the weighing-head by 
means of nuts at each end of long bearings, one on each side, are seen the 
two horizontal reaction-bars, on which are cut continuous screw-threads. 
These form the rigid connection between the fixed weighing-head and the 
movable straining-head, through which they pass in smooth bearings placed 
sufficiently far apart to allow room—with several inches of clearance-space— 
for two large abutment-nuts, one on each screw. These nuts may be revolved 
simultaneously, by suitable mechanism, to produce motion for adjustment of 
the straining-head in either direction for different lengths of specimen. 

The cut shows the machine ready for a compression test, the two com¬ 
pression-platforms, the one on the end of the draw-bar of the weighing-head, 

* For a paper by J. Sellers Bancroft, on this machine, with full illustrations, see 
Erujr. News and Am. Machinist, both of March 22, 1894. 

fin this term the word “strain” is used as meaning deformation under stress. 
Thus the elongation (or compression) is all produced by the moving of this head to the 
right or left, thus producing the straining, or deforming, of the specimen. 





332 


THE MATERIALS OF CONSTRUCTION 


the other on the end of the straining-bar, or piston-rod of the straining- 
head, also being plainly visible. With a compression specimen between the 
two heads the tendency is to move these apart, and the reaction-screws will 
then be in tension, requiring the abutment-nuts to be—as shown in the cut 
—up against the front bearings of the straining-head. With a tension 



specimen between the heads the tendency is to pull them together; the reac¬ 
tion-screws will then be in compression, and the abutment -11 uts set up 
against the rear bearings of the straining-head. 








TENSION TESTS. 


333 


On the sudden breaking of a tension specimen the reaction-screws will 
suddenly relieve themselves of their compressive stress by pushing the heads 
of the machine apart with sufficient force to set both in motion along the 
bed. The motion of the straining-head is gradually destroyed by its own 
friction against the bed, and in a distance which under all circumstances is 
well within the clearance-space that the abutment-nuts have between the 
sleeves for the reaction-screws, while the motion of the weighing-head is also 
checked by the projecting ends of these screws butting against powerful 
springs that are locked up under heavy pressure in suitable box-castings 
rigidly attached to the bed, as clearly seen in the cut, these springs also being 
strong enough to return the head to its original position. The arrangement 
of these recoil-springs in their boxes and about the projecting ends of the 
reaction-screws is such that they resist motion of the weighing-head in either 
direction, and also tend to return it to its original position after a recoil in 
either direction. Machines of 100,000 lbs. capacity are of simpler construc¬ 
tion. 

Passing now to the actual construction of the weighing-head, the vital 
part of the machine, we have in Fig. 267 a horizontal section of a weighing- 
head showing the arrangement of the hydraulic support and other details. 
As indicated by the arrows, the machine is supposed to be in operation on a 
tension specimen, and to facilitate the study of the relation of the various 
parts the exceedingly small movements that take place between some of 
them have been enormously exaggerated. The hydraulic support has also 
been represented in a somewhat simplified form, which would be satisfactory 
for machines of small capacities but for certain difficulties of handling dur¬ 
ing construction. The parts marked A and B are the two main castings of 
the weighing-head, which are securely bolted together, as well by the reac¬ 
tion-bars or screws C , in a manner clearly shown in the figure, as by several 
intermediate bolts on their circumferences, as shown in Fig. 268. Thus 
bolted together they form an exceedingly strong and stiff beam, enabling the 
stress exerted by the specimen to be returned to the straining-head through 
the reaction-bars . The central member marked D is the draw-bar , to which 
are screwed the two draw-bar heads A and F. The draw-bar with its two 
heads is kept in position relatively to the main castings A and B by the 
annular steel plates G, which on their outer edges are centred in and securely 
clamped to these castings by means of the annular washers ZTand numerous 
bolts /, and which in turn centre the draw-bar by their inner circumferences 
and are securely clamped to its heads by the annular washers J and numerous 
bolts K. Through their flexibility these steel plates will be seen to allow 
the draw-bar. with its heads, a certain freedom of motion axially, while they 
fully maintain its concentric position with the main castings A and B. 

The annular castings L and M surrounding the draw-bar between its two 
heads, and secured to and centred by it by means of annular steel plates P, 
annular washers, and numerous bolts, in a manner similar to that in which 
the draw-bar itself has just been described to be secured to the main castings 



Fig. 267.—Horizontal Section of the Weighing-head of an Emery Testing-machine. (Barth.) 
























































































































































































TENSION TESTS. 


335 


A and B , are respectively the cylinder and plunger (more properly the bear¬ 
ing-plates), or blocks, of the hydraulic support, which is thus seen to be 
annular in the actual machine, and not circular as the one shown and 
described in connection with Fig. 2G5. The parts marked and 0 are two 
annular washers that clamp the edges of the thin brass diaphragms composing 
the sack to the bearing-block Z, the liquid being confined between these 
diaphragms, as also already described in connection with Fig. 265. The two 
plates forming this closed sack are not soldered together. They are simply 
held by the great stress in the bolts which bind the washers N and 0 so as 
to maintain a tight joint under the maximum pressure. The pipe forming 
the communication between the hydraulic support and the reducing-chamber 
of the scale is marked R. 

The draw-bar heads E and F are provided with a number of external 
projections or spur-ribs, £7, extending into cavities in the main castings A 
and B , as may be seen in the case of the head E and the main casting A . 
The cavities in A and B leave between them an equal number of projections, 
V, which extend back into the cavities between the ribs U on the draw-bar 
heads, as may be seen in the case of the head F and the main casting B. 
The arrangement of these ribs and cavities, which enables a machine with a 
single hydraulic support to be used both for tension and compression tests, 
will be better understood from Fig. 268, in the right-hand view of which 
this is made perfectly plain. 

The manner in which the pull on the draw-bar is transferred by the ribs 
on the head E to the bearing-block from this through the liquid-sack over 
to the other bearing-block M, and finally from this to the ribs on the main 
casting B , will now readily be understood, and it will also be seen that a 
push on the draw-bar, due to a compression test, would in a similar manner 
be transmitted by the ribs on the head F over to the annular bearing J/, 
from this through the liquid over to the corresponding bearing L , and finally 
from this on to the ribs on the main casting A. 

Owing to supposed internal strains and stresses in the diaphragms of the 
hydraulic support, it has been found necessary to put about 50 or GO lbs. per 
square inch initial pressure on the same, the levers of the scale having then 
first to be balanced by means of a suitable weight that can be slid along a rod 
attached to the poise-frame lever before beginning a test. This initial 
pressure on the hydraulic support is obtained in the smaller machines by the 
device shown in Fig. 267, while in larger machines a very complex device is 
used to get the requisite pressure, the principle of this, however, being essen¬ 
tially the same. The device as here shown consists of a large fiat spring S, 
attached, in a manner clearly seen in the figure, to the projecting ends of the 
reaction-bars, and forming the bearing for a screw, T , secured against end 
motion in this bearing by a collar attached to it on the inside of the spring, 
and by the capstan-head W fastened to it by a key and a nut in the cus¬ 
tomary manner on the outside of the spring. This screw fits into a tapped 
hole in the end of the draw-bar; and it will be understood that if the capstan- 


336 


THE MATERIALS OF CONSTRUCTION. 



Fig. 268.—Vertical Sections of the Weighing-head of an Emery Testing-machine. (Barth.) 

















































































































































TENSION TESTS . 


33 ? 


head be turned in the direction of the arrow, the tendency is to move the 
draw-bar, with it its heads and the whole hydraulic support, away from 
the spring, until the hearing-block M brings up against the ribs on the main 
casting B , further turning producing a bending of the spring in the opposite 
direction. The resistance of the spring to this bending is then transmitted 
through the screw T, the end of the draw-bar, the ribs on the head E , the 
bearing-block Z, the liquid, and finally the bearing M over to the casting B. 
This condition of affairs is exactly what is brought about before beginning a, 
tension test, for which the machine is supposed to be represented in this, 
figure. A sufficient turning of the capstan-head in the direction opposite to 
that indicated by the arrow will similarly pull the draw-bar, etc., towards 
the spring B until the cylinder L is brought up against the ribs of the main 
casting A; a further turning bending the spring towards the end of the 
draw-bar. This, with its consequences, is the condition of affairs brought 
about before beginning a compression test. 

It will be seen that the spring S is provided with a stop, to match a, 
similar stop on the capstan-head to bring up against, for the purpose of 
limiting the motion of this latter in either direction, the pitch of the screw 
T being so selected and the wdiole device so fitted up that the determined 
amount of bending of the spring in the one or the other direction will pro¬ 
duce the desired amount of initial pressure on the diaphragm of the hydraulic 
support. The total possible movement of the hydraulic support in its cham¬ 
ber, between the attached heads A and i?, is only 0.006 in., so that the 
maximum movement from a mean position is only 0.003 in. 

Fig. 268 is a vertical section of a weighing-head, in which the hydraulic 
support is shown in its most improved and complete form, the initial pressure 
device being, however, of the same type as that already described. It will 
be seen that the annular bearing-block M is here not supported on the draw- 
bar D directly, but that it is in the first place fixed in its proper relation to 
the bearing-block Z, independently of the draw-bar, by two annular steel 
plates, rigidly clamped in the usual manner; and that it is also bolted to 
another large annular casting F, which is supported on the draw-bar in the 
same manner as the bearing-block Z. In addition to this casting V there 
is also seen another annular casting X, a small arc of the circumference of 
which is provided with gear-teeth meshing with the teeth of the pinion Y 
on the end of the hand-lever shaft Z. It may thus to a limited extent be 
rotated in the one or the other direction, but it is otherwise confined between 
the main casting A and Z, and also to be centred on A by a circular tongue 
and groove. The plates X and Fare on the figure shown to be in contact, 
and the contact surfaces are helicoidal or screw-shaped, so that rotation of 
X in one direction tends to force them apart, and to bring F up against the 
ribs of the casting Z, while rotation of X in the opposite direction leaves V 
with a little play between X and Z. The latter of these conditions is 
brought about by the operator before beginning a compression test, the 
former before beginning a tension test. The purpose of this arrangement is 


338 


THE MATERIALS OF CONSTRUCTION . 


to protect the diaphragm of the hydraulic support from the great shock it 
’would otherwise receive by the sudden release of the stresses on the various 
parts of the weighing-head, on the sudden breaking of large specimens when 
a powerful recoil of the draw-bar occurs. With the annular anvil V set up 
tight against B by the annular wedge JT, the energy of this recoil is trans¬ 



mitted directly over to the main casting A without passing through the liquid 
support and the diaphragm, on which an exceedingly high pressure would 
otherwise be produced, which if frequently repeated would finally destroy it. 

In Fig. 209 is shown on a larger scale a section of the annular hydraulic 
support on one side of the draw-bar only, which, without any further explana- 


Draw-bar in an Emery Testing-machine. (Barth.) 












































































































































TENSION TESTS. 


339 


fcion, will serve to give a clearer idea of the detailed arrangement of the 
diaphragms and the surrounding parts, and also the manner in which the 
pipe i?, which forms the communication between the hydraulic support and 



the corresponding reducing-chamber on the scale, is attached to the former. 
The two plates which form the sack lie flat against the hearing-blocks, 
underlaid, however, by connected grooves, their edges being held so tight by 















340 


THE MATERIALS OF CONSTRUCTION. 


the bolts B as to prevent all leakage. The plate on the left side of this 
sack is cut away and spun into an annular pocket in the auxiliary block W 9 
and it is made tight to it by running in a solder. To this auxiliary block 
is now attached the connecting pipe R as shown. This pipe is first soldered 
to a screw-plug which has a spherical front which bears on the conical bottom 



Fig. 271.—The Riehle-Marshall Extensometer. 


of the opening in II, so that by screwing up hard a perfect joint is made by 
the elastic deformation of the metal at the surface of contact. 

In Fig. 270 is shown the form given to this machine when made with a 
capacity of 100,000 lbs. 

274 . Extensometers.—There are three general types of extensometers 
in common use, viz., Double Micrometer-screws with Electric Contact3 


















































































































TENSION TESTS. 


341 


Friction-rollers with Dial Indicators; and Bauschinger’s Mirror Apparatus. 

The micrometer-screw extensometer was developed and perfected by Mr. 
C. A. Marshall, M. Am. Soc. C. E.,* and it is now manufactured, with some 
improvements, by Rieliie Bros, as shown in Fig. 271 . The essential features 
of all these extensometers are: 

1 . Measurements are taken on opposite sides of the specimen, between 
symmetrically placed points on rigid collars which are attached to the speci¬ 
men by screw-points or knife-edges lying in two transverse planes a known 
distance apart. 

2 . The measurements must be taken to the nearest inch. 

3 . The apparatus must be removable with¬ 
out releasing the load on the specimen. 

In the Marshall Instrument the collars 
are open, thus enabling them to be removed, 
and also giving to them a sufficient spring to 
take up the reduction in the diameter of the 
specimen as it elongates. The elongations 
are read on micrometer-screws to 0.0001 
inch, the contact being determined by the 
ringing of an electric bell on the closing of 
a circuit by the contact. With a low but 
constant current this contact-distance is 
found to be constant within the limit of read¬ 
ing given above, f Both screws are read after 
each increment of loading, and the average 
movement taken as the stretch of the speci¬ 
men. This is a most excellent and delicate 
instrument and is very largely used. It has 
the advantage of a more positive and direct 
measurement of the deformation of the speci¬ 
men than either of the other forms. 

The extensometer havin g friction-rollers 
with dial-indicators , shown in Fig. 272 , is a 
modification of one of Bauschinger’s forms, 
as made and used by the author. J It operates 
by means of two axles, having friction-rollers 
at one end and a vernier-needle at the other 
which moves over a graduated dial. The 
friction-roller is just 0.5 inch in circumference, and the dial is graduated to 
500 divisions. The vernier on the end of the needle reads readily to 0.1 of 



Fig. 272 —The Author’s Exten¬ 
someter. 


* A brilliant young engineer, a friend and college-mate of the author’s, who lost his 
life in the great Johnstown flood, 1889. 

f By using a resistance relay in the circuit a strong current may be made to pass 
through the bell, and a weak one through the contact points. 

X Manufactured by Malm & Co. of St. Louis, Mo. 























































































































342 


THE MATERIALS OF CONSTRUCTION . 


a division, thus giving readings to 0.0001 inch. The collars are attached 
by three screws, and removed by opening them by a hinge movement. 
One of the screws has a spring bearing in the collar to take up the shrink¬ 
age of the specimen when under stress. 

The friction-rollers are actuated by means of two arms which have a spring 
bearing upon them, the opposite ends being rigidly attached to the opposite 
collar in each case. Thus while the needles move in the same direction any 
bending of the specimen, or angular movement of the collars with respect 
to each other, is eliminated in the mean of the two readings, the same as 
with the Marshall apparatus. The needles are delicately mounted so as to 
have very little friction, and experience shows that the friction-contact is 
•entirely reliable. 

The advantages of this form of extensometer are: 

1 . It shows by its movements the deforming action of the specimen, 
which is a great advantage for students. 

2 . It is equally suited to measure large deformations beyond the elastic 
limit as it is to measure the extremely small movements inside that limit. 

3. It is equally adapted to compressive and tensile tests. 



Fig. 273.—Diagrammatic Plan of Bauscliinger’s Minor Extensometer. 


4. It is adapted to all lengths of specimens by simply changing the side 
arms, several pairs of which go with the instrument.* 

5. On releasing the load it shows the permanent set without any manip¬ 
ulation. 

6 . It never needs to be touched by the observer during a test, which is a 
great advantage in making such delicate measurements. 

7. After passing the elastic limit, and under a given constant load, the 
continued movement of the needle indicates the time-effect of such loads 
and when such cold-flowing has practically ceased. 

If the specimen should unexpectedly break with the apparatus on, no 
great harm results. At most some of the clamping-screws may be bent, but 
these cost little to renew. 


* The author has used it successfully for observing the effects of moving loads on 
bridge members, with arms five feet long, covered with thin rubber at their roller ends, 
and specially made U-shaped clamps instead of collars. 
















TENSION TESTS. 


343 


Bausellingcr’s Mirror Apparatus is shown in Figs. 273 and 274. The 
specimen is clamped at two points, as shown at (5), Fig. 274, and at a and b , 
Fig. 273. The stretch of the specimen is fully represented by the turning 
of the friction-rollers r, and r 2 , these being rigidly attached to the mirrors 
m, and m , through the arms a l and & a . The screws set back of the mirrors 



Fig. 274.—Bauschinger’s Mirror Extensometer Apparatus. Fig. 275. 


are used to adjust them to a zero-reading on the scale, which is reflected into 
telescopes as shown in Fig. 273. 

For simply observing stretch for the purpose of detecting the elastic limit 

with reasonable accuracy, the Paine extensometer, Fig. 275,* may be used 

_ _____ » 

* Designed by W. H. Paine, M. Am. Soc. C. E., and used by him for finding the 
elastic limit of the steel wire used on the New York-Brooklyn suspension bridge. 
Made now by Riehle Bros. 





































































































































































344 


THE MATERIALS OF CONSTRUCTION. 



with advantage. Its multiplication is usually made about 20 to 1, and it 
may be read by vernier to 0.0001 inch, though it is usually made to read 
only to 0.001 inch. This instrument has also been used to obtain the 

stretch of bridge-members under 
moving loads. As it measures 
stretch on only one side of the 
specimen, its indications must 
not be accepted as absolute, 
especially inside the elastic limit, 
while its capacity is very small 
beyond the elastic limit. 

Mr. Gus. C. Henning has per¬ 
fected a simpler form of this 
apparatus.* Fig. 276 shows the 
mirrors and their attachments 
to the specimen. 

275. Autographic Stress-di¬ 
agram Appliances.—These fall 
into two general classes : 

1 . Those in which the load 
coordinate is recorded through 
a movement of the poise on the 
weighing-beam. 

2 . Those in which the load 
coordinate is recorded through 
the lifting of the weighing-beanr 
against the increasing resistance 
of a calibrated spring attached 
to its free end. 

The deformation coordinate 
is in all cases multiplied either 
by levers or by the principle of 
the cone-pulley. The paper is 
usually attached to a cylinder, 
although it has sometimes been 
attached to a plane board. The 
pencil usually moves in a straight 
line, indicating one of the two 
Fig. 276. Henning’s Mirror Extensometer. coordinates, while the cylinder 

(or board) moves to register the other function, and it matters not which 
of the two movements is made by the deformation of the specimen and 
which by the increasing load. The location of the paper and its mounting 


* See Trans. Am. Soc. Mech. Engrs., vol. xvm. p. 849, fora full, illustrated description. 














TENSION TESTS. 


345 



Fig. 277.—Henning’s Autographic Portable Extensometer. 























































































346 


THE MATERIALS OF CONSTRUCTION. 


is a matter of convenience simply. The cords (or wires) which are to 
transmit the stretch of the specimen must form a pair, symmetrically 
placed on opposite sides of the specimen; they must be attached to one 
collar and pass through pulleys similarly placed on the other. They should 
then pass off in a plane at right angles to the specimen * and connect with 
the ends of an “evener” (lever), to the centre of which is attached the 
single cord which passes either to the pencil-holder or to the cylinder 
which carries the paper. If cords are used, they should be such as do not 
stretch appreciably for such changes of stress as occur in them during the 
test. 

One method of mounting these parts is shown in Fig. 256 (Olsen’s) 
and another form in Fig. 258 (Kiehle’s). In both cases the pencil is 
moved by the poise by means of a reducing-gear, and the cylinder is 
moved by the deformation of the specimen by means of a multiplying- 
gear. 

The autographic extensometer shown in Fig. 277 is portable and can be 
used on any machine having a poise moving upon a weighing-beam. It is 
designed and manufactured by Mr. Gus. C. Henning, M. E., New York.f 
It is self-contained, the record-cylinder being mounted directly upon the 
specimen. It is adapted to give accurate stress-diagrams in both tension 
and compression, and is said to work ecjually well in a vertical or in a 
horizontal position. The pencil has a parallel motion, and the recording 
cylinder can be mounted upon either side. The specimen is clamped with a 
spring bearing, to take up the reduction in the thickness when pulled 
beyond its elastic limit. It would seem to be a very complete apparatus 
and easily carried and set up. 

A great defect of all the autographic appliances given above is that 
they do not readily give the last end of the curve after passing the 
maximum load, although they would do this if the poise should be 
run back so as to keep the beam in balance at all times. This is a dif- 
cult feat with both the hand- and the electrically-controlled movement 
of the poise, and the result is that this part of the diagram is usually 
worthless. 

In the Gray Extensometer Apparatus,\ however, Fig. 279, this part of 
the curve is obtained perfectly, for the weighing-beam is at all times in 
perfect balance, since it pulls upon a calibrated spring. Here the pencils 
are moved at two rates of speed by the deformation of the specimen, and 
the cylinder is turned by the lifting or dropping of the weighing-beam. The 
long trussed lever at top gives a movement to one of the pencils of from 

* This is necessary in order that the stretch of the specimen may be fully repre¬ 
sented in the shortening up of the cord. The cords should therefore be attached to the 
moving end of the specimen. 

f See description in Trans. Am. Soc. Meek. Engrs. y vol. xvm. p. 823. 

\ Designed by Prof. Thos. Gray, and manufactured by Riehle Bros, 



Fig. 279. —Showing ihe Gray Extensometer Apparatus mounted on a 200,000 lb. Testing machine. 


TENSION TESTS. 


347 































































348 


THE MATERIALS OF CONSTRUCTION. 


one to two times the actual deformation between the collars, while the other 
trussed lever may give to the other pencil a movement from one hundred to 
five hundred times the actual relative movement of the collars, depending 
in each case on the link connections which are made preparatory to start¬ 
ing the test. Furthermore, both pencils operate inside the elastic limit and 
some distance beyond, when the one moving more rapidly is automatically 
thrown out of gear, while the other pencil proceeds to record the complete 
diagram on the smaller scale. The result is a double stress-diagram, such 
as shown in Fig. 5. The diagrams shown in Fig. 280 have been photo¬ 
graphically reduced directly from autographic diagrams made by this appli- 



Fig. 280.—Tension-stress Diagrams of Low Carbon-steel automatically recorded by the 
Gray Apparatus. (Made by Prof. Gray for the author.) 

ance for the author by Prof. Gray himself. They do not extend beyond the 
yield-point stage of the test. 

Mr. Olsen's new Micrometer' Autographic Attachment forms a supplement 
to his general stress-diagram apparatus, for the purpose of making a diagram 
inside of and somewhat beyond the elastic limit, in which the stretch of the 
specimen is magnified five hundred times. He accomplishes this by revolving 
the drum one hundred times as fast inside the elastic limit as is done beyond 
that limit, the stretch of the specimen here being greatly multiplied by a 
micrometer-screw and its accompanying gearing shown in Fig. 281. When- 


















































TENSTON TESTS. 


349 


ever the collars separate, the lower pair of fingers (being weighted) drop 
with the lower collar and so break an electric spring-contact shown on the 
left of Fig. 281, which sets in motion both the drum carrying the paper (not 
shown here) and the micrometer-screw and its gearing, which at once closes, 
the circuit by raising the outer end of the lever to which the spring-contact 



is attached. A very large circumferential motion can thus he obtained for 
a very small movement of collars (500 to 1), and this can be conveyed by a 
positive connection to the drum of the autographic apparatus. When the 
elastic limit has been passed this part of the apparatus is thrown out of gear, 
the drum set back to its proper position under the pencil for the small-scale 




























































350 


the materials of construction. 


diagram (deformation 5 to 1), and the test proceeds to its completion at the 
final rupture of the specimen. The poise is moved either forward or back¬ 
ward at pleasure by making the proper electric connections, or both these 
connections can be made at once, in which case the poise moves forward when 
the beam is up, and backwards when it is down. The last part of the diagram 



can thus be obtained. The entire machine, with both the large- and the 
small-scale diagram apparatus, is shown in Fig. 282. 

276. Micrometer-callipers.—In Figs. 283, 284, and 285 are shown three 
forms of micrometer-callipers, one or more of which are necessary for accu- 


















































































































Fig. 285. 


TENSION TESTS. 


351 



>-» , U\ W [J 

u 0) O' 'J tn 

• 09 tj O' 

£ M U 1 


S^S-^ tetjh* 

u S 2 h«- 

L. »“ 






w £co viwioa 


m^S £ 
M?ttW 

N Usl 


Oo ►- Ui co w 
“ a O! w « 
N>jI 3N to 





















































































































































































































































































































































352 


TEE MATERIALS OF CONSTRUCTION ,. 


rately measuring the dimensions of test specimens. The form shown in Fig. 
283* spans 8 inches; that shown in Fig. 284 spans 2 inches, and that in 
Fig. 285 spans 2j inches, all of them reading to 0.0001 inch. The advan¬ 
tage of the last form is that one may be set for the width and the other for 
the thickness of plates, thus saving much running back and forth of the 
micrometer-screw. 

277. Gauging-implements.—It is common to lay off the test specimen 
into 1-inch divisions either by scratch-awl or centre-punch marks. For the 



/r 


_ 




Fig. 286. 


former (used on plate specimens) the laying-off gauge shown in Fig. 286 is 
used, and for the latter (used on round specimens) the double-pointed 



Fig. 287. 


centre-punch shown in Fig. 287 is most convenient. Some such instru¬ 
ments are essential to accurate work, and they also are great time-savers. 


* Designed by Prof. Sweet and made by the Syracuse Twist Drill Co., Syracuse, 
N. Y. 


















































CHAPTER XVI. 


COMPRESSION TESTS. 

278. Objects of Compression Tests. —While tension tests are made for the 
purpose of determining many of the more significant mechanical properties 
of the malleable metals, compression tests are made to determine resistance 
to compression alone. In Chapter III it was shown that the materials of 
construction divide themselves into two general classes with respect to their 
manner of failure in compressive tests, these two classes being called plastic 
or viscous materials, such as the malleable metals, and brittle or oomminuible 
materials, such as cast iron, stone, brick, etc. 

When testing plastic materials in compression the “ apparent elastic 
limit” must be regarded as the ultimate strength; and since this limit in 
compression is in nearly all cases the same as it is in tension, it is commonly 
taken as the same, and no compression tests are made on such materials except 
when made up into full-sized columns. The compression tests of these are 
known as “ tests of columns,” rather than “ compression tests ” of that 
material. 

Brittle materials are tested in compression to determine their resistance 
to crushing. 

279. Compression-test Specimens. —In the case of metals the test speci¬ 
mens can be turned or shaped accurately, but in the case of stone, cement, 
concrete, brick, etc., if is not practicable to obtain perfectly true specimens, 
and hence some suitable provision must be made for these when placing them 
in the testing-machine. For such materials the form of specimen hitherto 
almost universally employed has been that of the cube. In Chapter 111 it 
was shown that this form is too short to give a normal failure; that the 
length in the direction of the applied load should be at least 14 times the 
least lateral dimension. It is probable, however, that compression tests will 
continue to be made on cubical forms, for the reason, that the results may 
thus be comparable with those hitherto obtained and published. The 
general relation between the strength of cubes and of prisms of various ratios 
of height to least breadth, for sandstone, is shown in Fig. 17, Chapter III. 

While perfectly true and parallel surfaces cannot usually be obtained, 
they should be made as nearly so as possible. This can be done at a small 
cost if stone-grinding works are at hand, or if such a special grinding-machine 
is available as that shown in Fig. 288. 


353 


354 


TEE MATERIALS OF CONSTRUCTION. 


The test specimen should be very nearly prismatic, since when the side 
protrude much beyond the bearing-surfaces the specimen is strengthened a 
shown in Fig. 18. 



Fig. 288. — An Abrasion Testing- 
macliiue. 



ding on the Strength of Sands*ou< 
{Inst Civ. Engrs., vol. evil.) 


280. Bedding the Specimen in the Testing-machine. —If the specime 
has not true and parallel beds, it is necessary to embed the specimen i 
plaster of paris. This is done by inserting sized paper between the plaster c 
paris and the specimen to prevent the absorption of water by the specimer 
which invariably weakens it if it has a high absorbing capacity. A sma 
load is brought upon the specimen while the plaster beds are soft, and thi 
is left on for some ten minutes or longer, till the plaster has hardened, whe 
the test proceeds to failure. Great care must always be taken to put the tet 
specimen accurately in the axis of the testing-machine. Compression test 
probably more often give erroneous results from not having done this tha 
from any other cause. 

If*the specimen has true and parallel beds, then it may be placed directi 
between steel plates, or between the machine cross-heads, if these are tru 
and smooth. Or single thicknesses of tar-board may be employed. In an 
case no bedding material must be used which will flow, like lead, or spread 
like wood, when the load comes on. This causes the specimen to split u 
and to fail in detail. (See Fig. 289.) 

An infallible test of nroper bedding and placing in the testing 7 machin 
is the manner of failure of the specimen. If it spalls off on the side 
(especially if it spalls mostly on one side) before final crushing down, some 






















COMPRESSION TESTS 


355 


thing is wrong. It should spall very little, and should crush down suddenly, 
with a great explosive sound, and fly over the room. 

An adjustable bearing-plate at one or at both ends of the specimen is 
desirable, but not strictly necessary if care be taken to secure in other ways 
a true initial bearing. 

281. Compression-test Machines. —The universal machines shown in Figs. 
256, 257, 258, 259, 260, 266, and 270 are all adapted to the making of 
compression tests as well as tests in tension. In Fig. 372 is shown a machine 
for compression (cement) tests only, and the author has had constructed a 
machine for testing timber columns, with a capacity of 1,000,000 lbs., which 
works in compression only, but in general all the compression machines used 
in America are of the universal type. 

282. Compressometers. —Since compression-test specimens are generally 
very short, the ordinary appliances used in tension tests for measuring 



deformations cannot be employed. In Fig. 290 a very convenient com- 
pressometer is shown, which is adjustable to varying heights of specimen by 
moving the geared pair of screws, and to specimens of excessive height by 
introducing new sets of screw-stems. The bearing-points are in pairs, 
mounted on rockers, so that any unsymmetrical movement is provided for and 
sliminated. It reads to T owo i n °h by electric contact at the right end, 
Linder the set-screw there. The deformation of the specimen breaks this 
contact, and by turning the micrometer-screw the contact is made, this being 
indicated by the ringing of a magneto-bell. 

For large specimens a form like that of Prof. 0. Bach, Fig. 291, may 
De used.* This measuring device consists of two rings, A A (on top) and BB 
(below), each of which is fastened to the specimen by means of four screws, 

* The description here given is taken from Zeits. d. Ver. Deutscher lngenieure, April 
5.7, 1895. 






























































































































356 


THE MATERIALS OF CONSTRUCTION. 





Fig. 291.—Bach's Apparatus for Compression Tests of Concrete Columns 10 in. dian 

eter and 40 in. long. 

































































































COMPRESSION TESTS. 


357 


being at right angles to each other at any convenient distance apart. (The 
apparatus shown in the figure was used on concrete cylinders 10 inches in 
diameter and 40 inches long, the rings being 30 inches apart.) 

The measuring apparatus is shown on the right. If a compression of the 
test specimen occurs, the upper terminal point of the rod, (7, which length 
remains the same, will move upwards a distance equal to the distortion of 
the specimen, thus causing the lever DEF to turn around its axis at E, and 
to carry along with it, by the small metallic thin ribbon fastened on its seg¬ 
mental end F, the axis G , on which the indicator is fastened, which latter 
runs along the arc graduation. The indicator is not pointed at the end, but 
flat, and upon it is an index-line, as may he seen in the drawing. The ratio 
is made so that 1 mm. compression of the test specimen equals 300 mm. 
distance on the arc scale. Since this can be read to y 1 ^ mm., the distortion 
of the measured distance can be read to mm * The only new feature 
of this instrument is the use of the thin metallic ribbon in place of gearing. 

The disadvantage of employing a rack and pinion was that the loads had 
to be varied by loading and unloading; the least lost motion would produce 
serious errors. Furthermore, the transmission proportion is dependent on 
the form of the tooth, for, being obliged to make the teeth so very small, we 
cannot depend on forming them sharp enough to maintain a constant trans- 
m ission proportion. * 

There should always be two such measuring instruments, set opposite 
each other, as shown in the general view on the left. By this method the 
measurement of the deformation takes place at two diametrically opposite 
points, the mean of the two readings being used.f 

For measuring given percentages of compression deformation of wood 
blocks of varying thicknesses, for instance, the author devised the apparatus 
shown in Fig. 292. Here a metal point, attached to a sleeve, moves on an 
adjustable inclined arm, so bent that the point moves on a line through the 
hinge in the plane of the flat base of the apparatus. The making of the 
contact at the point rings an electric bell, and the free movement of this 
point is interrupted by spring stops at such percentages of distortion as are 
to be observed (with the U. S. timber tests, in compression across the grain, 
these observed deformations were 3 per cent and 15 per cent of the thick¬ 
ness of the block). For a specimen of any height it is only necessary to 
move the point to its outer limit, raise it into contact with the upper com¬ 
pression-head of the machine, and tighten the thumb-nut. Then slide the 
point back to the first stop and proceed to load the specimen. When the 
bell rings note the load for that limit, and slip the point to the next stop, 
etc. 


* Where simple friction of a bar on a rolling pinion is relied on to move the indicator- 
needle, great care must be exercised, especially when loads are applied or released sud¬ 
denly. 

f These instruments are made by C. Klebe of Munich, Germany. 



358 


TEE MATERIALS OF CONSTRUCTION. 



Fig. 292.—Compressometer designed by the Author to Indicate two Conventional 
Limits of Deformation (3% and 15%) of Wood Blocks when Tested Across the Grain. 

4 



Fig. 293.— Tetmajer’s Compressometer for very short Specimens Tested in a Horizontal 
Machine. (Zurich Laboratory Communications, vol. iv.) 
























































































COMPRESSION TESTS. 


359 


283. Tetmajer’s Apparatus for Short Specimens.—In Fig. 293 is shown 
Prof. Tetmajer’s apparatus for measuring the deformation of very short 
specimens.* It is used in a horizontal (Werder) machine, and stands 
upright as in the figure. The compression of the specimen is taken up on a 
micrometer-screw which operates on the short arm of the indicator, the long 
arm of which actuates the upper, balanced, horizontal lever, thus bringing it 
to its zero position as shown by graduation lines on its left-hand end, and on 
the adjoining fixed portion of the frame. Because of the measurements 
being taken on one side only, and that a long distance from the specimen, 
the readings, while giving true relative motion, would probably not be true 
absolutely. Tetmajer used it mainly to determine elastic limits. ITis read¬ 
ings were taken to 0.0001 inch, and great care was taken in centring the 
specimen in the testing-machine. 

284. Compression Tests of Columns.!—Since the strength of a long 
column consists in its resistance to bending, rather than in its resistance to 
crushing, it follows that the strength of a straight column is a function of— 

1 . The elastic rigidity (modulus of elasticity) of the material, E. 

2 . The ratio of its length, /, to the rigidity function of its cross-section, 

which is the radius of gyration, r, that is, —. 

3. The character of its end bearings as to their tendency to hold the 
column to its original position, and 

4. The eccentricity of the loading. 

For a straight column, symmetrically loaded, supported at its gravity 

axis, and so as to be perfectly f ree to bend, and for a ratio of sufficiently 

large, it is shown in works on mechanics (and in the author’s “ Modern 
Framed Structures ”) that Euler's Formula gives the strength of the 
column. This formula is 


P = 


71 * E 



X 


where p = ultimate strength of the column, in pounds per square inch; 
E = modulus of elasticity, in pounds per square inch; 
l — length of the column between the pivot-bearings, in inches; 


* Described in Tetmajer’s Communications, vol iv. (1890). 

f It does not fall within the province of this work to enter into a general discussion 
of the strength of columns. The following is given as supplementary to what is usually 
found in the works on applied mechanics, and on framed structures, on this subject. 

\ While this is the only purely theoretical columu formula which is true in practice, 


it is only applicable to very long columns > 150 for pin ends, and ^ > 200 for flat eudsj, 

such as are seldom or never used in actual structures, and hence it is of little practical 
value. This form ila must never be used for the ordinary lengths. 




360 


THE MATERIALS OF CONSTRUCTION. 


r — least radius 
inches. 


of gyration of the cross-section of the column, in 


mm 


7m 























/ 

— 

rv 






or 1 f 

w/ 

/ / 



Njf 

CO 




k , 4 


i. nf 

y 





-O 


wfp 



/ 








) 





\ % 



III 1 









a 


wrc 


'4M?/c 

w 

.7c 

/]/ 

WOTS 












" .tsu 

VOL'C/Cr 

W7$7 



Ml 

7/76 

kJ 

747/. 

dcST/C 

Z77 





coMy 

1E0L 

ay 







V, 

Jifl/6 

r ffC 

7m 

£N'> 

r 7/ 

* C, 

IBB 

ON 

/A/ 

<ST£ 

££ 


7 7/ 72 76 74 77 77 77 77' 77 77 

Fig. 294.—Variation of Moduli with increasing Percentage of Carbon in Steel. {Wat. 

Ars. Rep., 1886.) 

In Fig. 296 the locus of this equation is shown for E — 30,000,000, the 
coordinates being p and —. 

Theoretically, for a perfect column, centrally loaded, the strength is con¬ 
stant for increasing lengths, this strength being the “ apparent elastic limit ” 
or “ yield-point ” of the material ( see Fig. 294) until the critical length is 
reached under which the column bends indefinitely under its maximum load, 
when for any further increase in length the load which will produce this 
bending regularly diminishes in accordance with the law of Euler’s curve. 

The theoretical locus, therefore, for the value of p plotted to - would be a 

r 

horizontal line at the apparent elastic limit of the material, extended to an 
intersection with Euler’s curve, and then down along this curve indefinitely. 
But because no column is perfectly straight, nor, perfectly free to turn, nor 






































COMPRESSION TESTS. 


361 


loaded and supported exactly in its gravity axis, nor has the same modulus 
of elasticity in all its parts, nor is of exactly uniform cross-section, etc., it 
follows that any locus derived from experiment would usually fall below this 
theoretical locus, and could never rise above it except from a higher modulus 
of elasticity, or from a higher elastic limit, or from more fixed end condi¬ 
tions than had been assumed. 

In making tests of metal columns there are but two conditions of end 
supports to which any theory can be adapted, these being rigidly fixed in 
direction and absolutely free to revolve. As it is impossible to satisfy the 
former condition, the latter becomes the only one to which any theoretical 
formula should be expected to conform. It seems remarkable, therefore, 
that, so far as the author is aware, there has been but one set of observations 
made which has fairly satisfied this requirement , these having been made by 
M. Considered Ingenieur-en-chef des Fonts et Cliaussees ,* France. Both 
Prof. Bauschinger and Prof. Tetmajer attempted to satisfy this condition, 
but they mounted their columns with cone or knife-edge bearings at the 
computed gravity axes, while M. Considere mounted his with lateral-screw 



Fig. 295.—Considere ’s Mounting for Column Tests. (Fr. Com. Rep., vol. hi. p. 124.) 
adjustments, as shown in Fig. 295, and arranged a very delicate electric 
contact at the side so as to indicate a lateral deflection as small as 0.001 mm. 

* First reported in 1889, and described in vol. i. p. 128 and vol. hi. p. 124 of the 
Report of the French Commission on the Methods of Testing Engineering Materials, 1895. 














































362 


TEE MATERIALS OF CONSTRUCTION. 


He then applied moderate loads to the columns and adjusted the end-bear¬ 
ings until they stood under such loads rigidly vertical, with no lateral move¬ 
ment whatever.* Then with his double knife-edge bearings at each end, as 
shown in Fig. 295, the columns were perfectly centred and absolutely free 
to move or turn about their end bearings, as the theory demands. With 
these conditions perfected he made 155 tests of columns, of various lengths 


from — = 40 to — = 346, and on various forms of cross-section. 
r r 



Fig. 296 — One Series of Results of M. Considered Column Tests, with Material having 
different “ Apparent Elastic Limits.” (Rep. Fr. Com., vol. m. p. 124.) 

In Fig. 296 the author of this work has plotted the tests made on solid 
rectangular steel bars, 10 rrfrn. by 17 mm. in cross-section, of six degrees of 

* This precaution is essential to a perfect test of the material of which the column is 
composed. Only in this way can other sources of weakness be eliminated. It is to the 
interest of the contractor, therefore, to provide these appliances. 




























COMPRESSION TESTS. 


363 


hardness. He has also fitted to these six sets of observations parabolic loci 
which cut the axis of loads at the respective “ apparent elastic limits,” or 
“ yield-points,” of the material,* and which are made to become tangent to 
Euler’s theoretical curve drawn for E — 30,000,000. The close agreement 
of these loci with their respective sets of observed ultimate strengths would 
seem to indicate that they cannot w r ell be improved upon, and that therefore 
this parabolic law may fairly be assumed to fit the actual facts in an ideal set 
of experiments as closely as it is possible to do.f 

It further appears from these curves that the coefficient of the subtrac¬ 
tive term follows a very definite law, as shown in “ Modern Framed 


Structures,” p. 150. Using this theoretical value of this coefficient, w 7 e 
have, as the maximum strength of any pivoted wrought-iron or steel column, 
in pounds per square inch. 


p = el. lim. 


(el. limy 




To show that the strength of a column is no function of the ultimate 
strength of the material either in tension or compression, M. Considere cold- 
rolled the medium hard steel in No. 5, which had an apparent elastic limit 
of 47,000 lbs. per square inch, until it had elongated ten per cent of its 
original length. This raised its elastic limit to 71,000 lbs. per square inch, 
while its ultimate tensile strength w r as raised only from 83,000 to 88,500 lbs. 
per square inch. Thus metal No. 6, with an elastic limit of 71,000 lbs. and 
an ultimate strength of 88,500 lbs. per square inch, was over 10 per cent 
stronger in columns than metal No. 8, which had an elastic limit of 64,000 
lbs. and an ultimate strength of 98,000 lbs. per square inch. 

While the parabolic curves here given are purely empirical in form, 
theory dictates: 

1 . That this locus shall start horizontally from the vertical axis at the 
“ apparent elastic limit ”; 

2. That it shall become tangent to Euler’s curve ; and 

3. That it shall have no points of inflection other than the point of tan- 
gencv with Euler’s curve. 

While there may be an infinite number of curves which would satisfy 
these requirements, the parabola is the simplest of all, and it also seems to fit 
the observations as well as any, whether these observations be made under 
ideal conditions, as in Fig. 296, or under the nearly ideal conditions of Prof, 
von Tetmajer, Figs. 297 and 298, or under the conditions of practice, as in 
Frn. 208 of “ Modern Framed Structures.” 


* As computed from the ultimate strengths which alone were given in the original 
communication, the yield-points not having been observed. 

f The author had already developed this curve as best representing the strength of 
ordinary columns too short for Euler’s formula to apply to, in “ Modern Framed Struc¬ 
tures,” p. 148 (1892). 





364 


THE MATERIALS OF CONSTRUCTION. 



W0f 


















































o so too ~7So"zoo ~Bd - 3od 

Fig. 298.—The Author’s Parabolic Column Formula fitted to Tetmajer’s Tests of Steel Columns. • (Communications , vol. iv.) 


COMPRESSION TESTS. 


365 

















































366 


THE MATERIALS OF CONSTRUCTION. 


Prof, von Tetmajer’s tests cover a great variety of forms, simple and com¬ 
posite, on both wronght-iron and steel, and the results of these tests are all 
plotted, with characteristic symbols, in Figs. 297 and 298. While these 
results scatter somewhat, owing to varying elastic limits of the specimens and 
to the fact that the knife-edge bearings were placed at the computed gravity 
axes, and were not adjusted to the true centres by lateral adjustment under 
small loads, as were those of M. Considere, still the parabolic curve fits the 
average position of the plotted points as well as could be desired. See also 
the similar diagram for wooden columns in Chapter XXXII. 

The following are the author’s parabolic column formulas as given in 
“ Modern Framed Structures”: 

ULTIMATE STRENGTH OF COLUMNS, IN POUNDS PER SQUARE INCH. 

For Wrought-iron Columns, Pin Ends , < 170,j 

V = 34,000 — .67 (^-j 2 .(2) 

For Wrought-iron Columns, Fled Ends, [^^210,] 

p = 34,000 - 

For Mild-steel Columns, Pin Ends, 

p — 42,000 — 

For Mild-steel Columns, Flat Ends, 

% 

p — 42,000 — 

For Cast-iron Columns, Flat Ends, 

p = 34,000 - 88—..(6) 


* This formula agrees very closely with the only actual tests of full-sized cast-iron 
columns ever made, namely those made at the Watertown Arsenal (Reports, 1887 and 
1888), and at Phcenixville, Pa., for the New York Building Department in Dec. 1897. 
(See p. 474.) These extremely low values of the ultimate strength of cast iron columns 
have been a great surprise to engineers and architects, and will probably result in the 
entire abandonment of cast iron in building construction. See also pp. 108 and 474. 









COMPRESSION TESTS. 


367 


For White-pine Columns, Flat Ends, ~ 60, 


p = 2500 - .6 (J) 


l __ 


For Short-leaf Yellow-pine Columns, Flat Ends, <60, 


■p = 3300 — .7 


• • • • 


Z - 


For Long-leaf Yellow-pine Columns, Flat Ends, < 60, 

IV 


p = 4000 - .8 (|) 


( 7 ) 


( 3 ) 


0 ) 


For White-oak Columns, Flat Ends, ( T < 60, 




p = 3500 - .8 Wj 


• • • 


( 10 ) 


To obtain from the above working formulae for designing, divide both 
teims of the right-hand members of these equations by the factor of safety 
chosen for the work in hand and for the material used. The smallest factors 
would be used with rolled mild steel, and the largest with timber and cast 
iron. 

285. Spring Testing-machines.—Fig. 299 shows a form of spring testing- 
machine adapted for both compression and tension tests, the former being 
made at A and the latter at B. It is made in two sizes, of 2500 and 4000 
lbs. capacity respectively. 

In Fig. 300 is shown a spring testing-machine of 65,000 lbs. capacity, 
for compression only, and not requiring the use of over-weights, although 
such are furnished for one half the total load, if desired. 




368 THE MATERIALS OF CONSTRUCTION. 



Fig. 299. —Spring Testing-machine for both Tension and Compression Tests, 



Fig. 300.—Spring Testing-machine 






















































































































































































































































































































CHAPTER XVII. 


CROSS-BENDING TESTS. 

286. Objects of Cross-bending Tests. —Brittle materials like cast-iron,, 
stone, brick, and concrete are tested in cross-bending to determine their 
ultimate strength, and perhaps also their resilience. Timber is so tested also 
to determine its ultimate strength and its modulus of elasticity. Springs and 
spring-steel are tested in this way to obtain their elastic limits and their 
deflections under given loads, and railroad rails are sometimes tested for 
elastic limit and ultimate strength. Cross-bending tests are also made for 
scientific purposes to test the correctness of the ordinary formulae for the 
strength and the deflection of beams. 

Since three kinds of stress, tension, compression, and shearing, are devel¬ 
oped when a beam is bent under the action of external forces, the problem 
is more complex than those considered in the two previous chapters. Usually 
the shearing stresses are left out of account in designing both for strength 
and stiffness, but the conditions under which this stress should be recognized 
and taken account of are given in Article 38, for strength, and Article 46, 
for deflection. 

287. Essential Considerations in Cross-bending Tests. —The essential con¬ 
ditions which must be satisfied in making cross-bending tests are: 

1. The loads should be applied centrally in the direction of the greatest 
or of the least moment of inertia of the beam, in order to prevent torsion. 

2. The supports must be rounded knife-edges, bearing on auxiliary 
plates if necessary to prevent indentation. 

3. The loads should be continuously progressive, without shock, and in 
the case of timber they must increase at a fixed rate with no stopping when 
readings are taken. 

4. The deflections must be measured by observing the movement of the 
neutral plane at the loaded point with reference to the neutral plane at 
the two end supports. That is to say, the deflection apparatus must be 
attached directly to the specimen, or rest on the end bearings, and be self- 
contained with the test specimen, and independent of all deforming move¬ 
ments of the machine itself. 

The fourth condition is seldom properly satisfied. It is common to 
measure deflections with reference to some part of the frame of the testing- 

3G9 


370 


THE MATERIALS OF CONSTRUCTION. 


machine, assuming this to be rigid, or by means of a deflection apparatus 
attached to this framework and moving with it. 



Cross-bending Testing-machines .—In the author’s machine, shown in 
Fig. 301, the deflection is measured by means of a micrometer-screw, 
reading to 0.001, inch held in place by a bar which is attached directly to 
the knife-edge bearings through parts which are not under stress. The 
micrometer-screw bears upon the top of the power screw which presses 
on the centre knife-edge. As all these bearings have steel plates intervening 
between them and the specimen (if this be timber), the movement of the 
centre bearing, with reference to the end bearings, is registered on the 
micrometer-screw, and this is the deflection of the specimen. One half the 
load is weighed on any ordinary form of platform-scales. 

In the large beam-testing machine of the author’s, shown in Fig. 302, 
used mostly for testing large wooden beams, the deflection is measured by 
means of a fine thread attached (at one end by a rubber band) to two nails 
driven into the stick in the neutral plane over the end supports. At the 
centre a nickel-plated scale, graduated to 0.1 in. and polished to act as a 
mirror, is fastened to one or both sides of the beam. The thread is then 
read on this scale by bringing it and its image into coincidence and esti¬ 
mating its position to the nearest 0.01 in. The load is applied by pumping 
oil into the cylinder below, thus depressing the screws and the cross-head 
carried by them, and one hal f the load is weighed on the 50,000-lb. plat¬ 
form-scales under one end. The base of this machine consists of two long- 
leaf yellow-pine sticks, 6x18 inches in section and 24 feet long, with a 
f X 18-inch steel plate inserted between them. Its capacity is 100,000 lbs. 

In the machine shown in Fig. 303, specially designed for cast-iron tests, 
the deflection is correctly indicated on the graduated arc by means of an 





























































Fig. 302.—Large Beam-testing Machine designed and used by the Author. 



LARGE BEAM TESTING MACHINE 

CAPACITYH0Q000LBS. 














































































































































































































































THE MATERIALS OF CONSTRUCTION. 


A72 


ingenious arrangement of levers underneath, not shown in the figure. Its 
-capacity is 4000 lbs. 

In Fig. 304 is shown Keep’s autographic recording transverse test appa- 



Fig. 303.—Cross-bending Testing-machine for Cast Iron. Deflection 

correctly measured. 


'■atus for his standard form of specimen \ inch square by 12 inches long. 
It makes an autographic record like those shown in Chapter XXIV, the de¬ 
flection of the test specimen being taken up by the gradual falling of the 
weighing-beam. The movement of the poise also moves the paper, while 
the deflection of the specimen moves the pencil. This is a valuable machine 
for tests on this size of specimen. 

The universal machines shown in Figs. 256 to 260, and in Figs. 266 and 
270, are all adapted to making transverse tests by inserting an I beam or 
other rigid base on the weighing-table when the specimen is longer than 
this, and supporting the specimen on it. 

288. Importance of Measuring the Deflection in Transverse Tests of Cast 
Iron. —The importance of measuring the deflection of transverse-test speci¬ 
mens of cast iron, as well as the breaking strength, is now generally recog¬ 
nized. The resistance of the metal to shock is measured by the product of 






















































































































































































































CROSS-BENDING TESTS. 


373 


the ultimate load into the final deflection, 
approximately the total area of the stress- 
diagram in cross-bending. If this be now di¬ 
vided by the volume of the metal between the 
end bearings, it gives resistance to shock in 
inch-pounds per cubic inch of metal.* Since 
it is more convenient, however, to weigh the 
bar than to compute its volume, the resistance 
to shock is commonly computed per pound of 
metal (between end bearings). 

From many experiments made by the author, 
he has recommended the following require¬ 
ments t for test-bars about 1 inch square: 

Inch-pounds per 
pound of Cast Iron. 

For the lower grades of castings.... 20-30 

For good machine castings.40-50 

For stove-castings, and for impact 

machinery.60-70 

In this way both the strength and the de¬ 
flection are properly allowed for; and since 
these results usually vary inversely with each 
other, both may vary greatly without showing 
an appreciable variation in this product, and 
hence without appreciably changing the value 
of the metal. On the other hand, the strength 
may be very high, with a very small resistance 
to shock; that is, it may be strong in a static 
test, but very brittle. These products will be 
greater for small (thin) specimens than for 
thicker ones; so the only safe rule is to find 
by trial what products can be expected and 
demanded for any given product and size of 
specimen. 

289. The Computed Strength in Pounds per 
Square Inch on the external fibres of a trans¬ 
verse-test specimen is found from the formulae 
given in Art. 33. Thus for any form of section 
tested to failure by a load at the centre the 
“modulus of rupture ” in cross-breaking is 



divided by 2, this being 


* It was shown iu Arts. 55 to 57 that the resilience was always proportional to 
the volume of the body subject to stress, it being independent of the dimensions of the 
body so long as the form of cross-section remained the same. 

f See a paper by the author on Cast Iron, Trans. Am. Soc. C. E., vol. xxii. p. 91. 







































































































































































374 


THE MATERIALS OF CONSTRUCTION. 


f - 

Jr j > 


• • (l) 


while for a solid rectangular cross-section 



3 Wl 


(») 


and for any form of cross-section we should have 





( 3 ) 


where f r — modulus of rupture in pounds per square inch; 

W — breaking-load at centre in pounds; 
l = length between end bearings in inches; 
b = breadth in inches; 
h — height in inches; 

y ) — distance from neutral axis to outside fibre which failed under 
the breaking-load, in inches; 

/ = moment of inertia of the cross-section about its neutral axis; 

M = bending moment on the beam at the section of rupture. 

Because these formulae are strictly true inside the elastic limit, it must 
not be inferred that this so-called “ modulus of rupture in cross-bearing ” 
represents any actual stress on any outside fibre, either in tension or com¬ 
pression, at the time of rupture. (See a discussion of this question in Arts. 
35 and 36, p. 50.) In general this modulus is about twice the tensile 
strength, in the case of cast iron, while in timber it is somewhat below an 
average of the tensile and the compressive strength of the wood. With this 
understanding this modulus is a convenient, though conventional, method 
of stating the strength of any material under cross-breaking stress, and for 
comparative purposes it is very useful. For the purposes of the designer, 
however, these formulae are strictly correct, since he always works with loads 
and stresses inside the elastic limits of the materials he uses. 

290. The Modulus of Elasticity (Stiffness) is preferably found from a 
transverse test, since it is mostly used for computing the deflection of beams. 
Since this quantity is of necessity computed from loads and their correspond¬ 
ing deflections inside the elastic limit, it follows that this modulus is found 
to be practically the same whether it is computed from tensile, compressive, 
or transverse tests. Thus Prof. Tetmajer tested fourteen rolled wrouglit-iron 
I beams, from 4 to 16 inches in depth, and obtained from them an average 
value of E — 27,840,000, while on thirty-one tension tests on specimens cut 
from shape iron from the same metal he obtained a value of E = 28,110,000; 
for wrought-iron riveted plate girders, from 16 to 28 inches deep, he ob¬ 
tained a value of E — 26,000,000. 


In mild steel he found 


For the tension specimens E = 30,550,000; 
“ riveted plate girders E — 28,160,000. 






CHAPTER XVIII. 


IMPACT AND HARDNESS TESTS. 

IMPACT TESTS. 

291. Object of Impact Tests. —As explained in Art. 53, impact tests 
cannot give absolute results, like those obtained from tension, compression, 
and transverse tests, and hence they are properly used only where other 
methods of testing are not available. They are commonly employed on cast- 
iron car-wheels, on cast-steel and malleable-iron car-couplers, and on car- 
axles and sometimes on rails and rail-joints. Axles and rails, however, can 
be tested statically in cross-bending, and more can be learned by testing them 
in this manner, by bending them back and forth, and plotting their bending- 
stress diagrams, than by the drop tests.* 

Because of the extreme difficulty of arranging an impact test so as to give 
to the specimen a plain tensile stress, without allowing a large and uncertain 
part of the energy of the blow to be absorbed in the auxiliary appliances, 
this has seldom been attempted, and certainly it never has succeeded in giv¬ 
ing any valuable results. 

Impact tests in compression are seldom employed except to produce pene¬ 
tration of a standard form, to determine hardness, which will be described 
later under the head of hardness tests. The impact test given to car-couplers 
might be called a compression test, perhaps, since the blow is given “ end-on”; 
but as failure here occurs by breaking off portions of the enlarged head, by 
developing in it excessive transverse stresses, it is really a transverse test. 

In general, therefore, impact tests are all transverse, or cross-bending, 
tests. 

The author has also introduced a species of impact test for street-paving 
brick in place of the abrasion test hitherto employed. This was done from 
the fact that paving-brick do not wear out by abrasion, but by being broken 
down by the blows from horse’s shoes, and from the wheels of vehicles. 

* An exception may have to be made in the matter of brittleness of metals induced 
by very low temperatures, which can, it is said, only be determined by impact or drop 
tests. 


375 




376 


THE MATERIALS OF CONSTRUCTION. 


Impact tests, therefore, are usually made to determine the resistance te 
diock of structural forms which cannot readily be tested in any other way. 

292. Essential Conditions of Impact Tests.—Since the force of a blow 
depends as much on the resistance ottered by the body struck as it does on 
the striking body, it follows that the anvil, or bed, of an impact machine is 
quite as important as the weight of the ram and the height of its fall. A 
standard impact test, therefore, involves a standard size of anvil and a 
standard froundation for it, quite as much as a standard weight of hammer 
and standard fall of same. 

The pendulum machine would seem to offer one advantage, however, 
which cannot be realized in drop machines. The pendulum machine can be 
so designed as to allow the pendulum weight to pass the specimen when it 
breaks, and by automatically recording its extreme movement, and deducting 
this vertical component from the original total fall, the actual energy absorbed 
by the specimen, up to rupture, would be determined provided the anvil is 
rigid.* In this way the specimen could be broken on the first blow, and the 
energy spent upon it (and absorbed by it) exactly determined. This would 
seem to be the only proper way to make comparable impact tests. 

The Pennsylvania Railroad Company has standardized the impact test 
of cast-iron car-wheels and of car-axles, and the American National Car- 
builders’ Association has now (189G) standardized the test for car-axles as 
indicated in Art. 294; but with these exceptions it can hardly be said that 
impact tests made in different places in this country can be considered as at 
all comparable, because of a want of identity in the foundation portion. If 
the impact machine be of the pendulum form, it must strike the specimen 
at the centre of percussion of the entire pendulum in order to prevent a 
portion of the energy from spending itself by bending the pendulum. 
While pendulum machines are more convenient, drop machines are more 
certain to deliver the full theoretical force of the blow. In a pendulum 
machine the energy of the blow is, of course, the total weight of the pendulum 
into the distance through which its centre of gravity falls. 

293. The Energy of the Blow.—The unit of measure in impact tests is 
the foot-pound (or kilogram-meter). This energy cannot be measured in 
pounds, and no scheme of equivalents can be devised between the foot-pound 
units of an impact test and the pound units of a static test , although this has 
often been attempted. There is no relation between the resistance to shock 
and the resistance to a static load, since there is no relation between the total 
area of a stress-diagram and its stress coordinate. The attempt which is 
often made, therefore, to equate these two kinds of resistance is as foolish as 
the ancient practice of estimating the discharge of a stream, or aqueduct, or 
pipe from its cross-section alone. 

From fhe law of the conservation of energy we have: 


* See Russell’s machine, p. 380a. 




IMPACT AND HARDNESS TESTS. 


377 


The work which gravity does on the falling weight, and which is wholly 
represented by the energy of the hammer at the time it strikes, ^ 

must be absorbed by the resisting body. This energy is equal, in 
foot-pounds, to the weight of the ram in pounds multiplied by 
its total vertical fall (including the vertical deflection of the 
specimen) in feet. 

In the case of a pendulum impact machine the entire weight 
of the swinging parts must be divided into two parts, and these 
parts concentrated at the axis of rotation and at the centre of 
percussion. The latter part, only, multiplied by its vertical 
drop is the measure of the energy of the blow (but this is the 
same as the total weight into the fall of its centre of gravity). 

To find the centre of percussion and the equivalent weight 
to be considered as concentrated at this point, a graphical solu¬ 
tion may be employed* as follows: q 

Let AG extended, Fig. 305, be the pendulum, with its axis C 
of rotation at A. Let G be the centre of gravity of the entire 
pendulum, with all its rigidly connected parts (to be found by Fig 3 q 5 
trial). Let GD , drawn perpendicular to AG at G, be made (to Graphical 
the given scale) equal to the radius of gyration of the entire Method of 
pendulum about its centre of gravity G , (to be computed). Finding the 

Then draw AD, and DC perpendicular to AD, cutting AG Ceiltre . of 
extended in C. Then is C the centre of percussion of the P eicuss i° n ' 
pendulum.* If the graduated arc (see Fig. 308) have a radius equal to AC, 
and the vertical components of the pendulum’s motion (versed sines) be laid 
off on this arc, then the equivalent weight to be concentrated at C is to be 
used for computing the energy of the blows, and this equivalent weight is 



or equivalent weight at 



IF:: AG 




W. AG 


AC 


( 1 ) 


where IF is the total weight of the pendulum used in finding the centre of 
gravity G. 

If the graduated arc has a radius equal to AG, then the total weight IF 
is to be used with the versed sine to compute the energy of the blow. 

If a conventional radius, R, has been used by the maker of the machine, 
then a corresponding IF r must be employed which will satisfy the equation 



WA G 
R 



In every case, however, the point of impact of the pendulum should be 
at C, the centre of percussion. 


* Rankine’s Applied Mechanics, Art. 581. 














378 


THE MATERIALS OF CONSTRUCTION. 



Fig. 306.- 


-Most Approved Form of Impact-testing Apparatus. (llep. French Com¬ 
mission. ) 




















































































































































































































































IMPACT AND HARDNESS TESTS. 


379 


294. Impact-testing Machines.—In Fig. 306 is shown the impact- 
machine designed and used by Prof. A. Martens in his testing laboratory at 
Charlottenburg, Germany.* Its dimensions are given in meters. It admits 
of an extreme fall of 4.5 meters (about 15'feet), and of a weight of ram of 
200 kilograms (440 lbs.), although he has used weights of 36 and 56 kilograms 
only. It is intended for specimen tests only. The anvil weighs 1250 kilo¬ 
grams (2750 lbs.), or 22.5 times the heaviest ram usually employed. This in 
turn is set on a strong cement-masonry foundation, separate from that of the 
building,! as should always be done with drop machines. 

The National Car-builders’ Association of America has (1896) adopted a 
spring support to the anvil, as shown in Fig. 307, in order to insure perfect 



Fig. 307.—Standard Impact-testing Machine with the Anvil-block on Springs, as 
recommended by the Master Car-builders of America, 1896. Previously used by 
the Penn. Iiy. Co. 

identity of reactions in different machines. This is perhaps the only way to 
eliminate the varying effects of different foundations of the anvil-block. 

Fig. 308 gives a view of Keep’s autographic recording pendulum impact- 

* See Mittheilungen a us den Koniglichen Technischen Versuchsanstalten zu Berlin, 
1891, p. 2, and Plate I. The machine was made by E. Becker, machinist, Berlin, 
f At first it was set on the floor, but it was found necessary to put it on a more solid 

foundation. 






























































































380 THE materials of construction. 

machine. It is used only for testing his standard cast-iron bars -k inch 
square and 12 inches long. The hammer weighs 25 lbs., and swings on a. 



Fig. 308.—Keep’s Impact-testing Machine. 























































































IMPACT AND HARDNESS TESTS. 


380 a 



CENTER OF 
GRAVITY 
OF KNIFE 


FLOOR 


LEVEL 


RCUSSION 


^CONCRETE FOUNDATIO 




* Evidently the particular character of this setting will greatly affect the force of the 
blow on the specimen. 

f Designed by Mr. S. B. Russell, M. Am. Soc. C. E., and fully described in Trans. 
Am. Soc. C. E., vol. xxxix. p. 237 (1898). Pages 380a and 3806 were added in the 
second edition, 1898. 


radius of G feet. The weight of the anvil is admitted to be too light, and 
the designer recommends that it be set against a brick wall ! * The arc is 
graduated to vertical drops of i inch, with a total fall of 6 inches. The 
paper on which the deflection is recorded at each blow is automatically 
moved T 3 ^- inch after each blow, so that the record consists of a series of 
parallel lines, each being the deflection for that blow, magnified four or five 
times by the leverage of the recording apparatus. 

In Fig. 308« are shown two views of the improved form of RusselFs 
pendulum impact machine.f The two knife-edge supports for the specimen 


Fig. 30Sa.— Russell's Impact Testing-machine. 

are separated by a free passage for the pendulum, so that by raising this 
higher than necessary to break the specimen on the first blow, the energy 
left in the pendulum carries it past a vertical position. By registering, or 



= =7|e= 


.. *«■ 

r f 

fry 


rf 

t !/ 

5jFT 


.. bi . 


Hzr'/ 

.. 











































































































380 b 


THE MATERIALS OF CONSTRUCTION. 


observing in any suitable manner, the final forward position of the pendulum 
after passing the broken specimen the residual energy left over after rupture 
becomes known. This subtracted from the potential energy due to the ini¬ 
tial position of the pendulum, and after making due allowance for the work¬ 
ing resistance to motion, leaves the amount of energy absorbed by the speci¬ 
men in the act of breaking it. The specimen supports are massive, and 
are firmly bedded upon a large body of concrete, so that they are very rigid. 
The centre of percussion of the pendulum is carefully determined and the 
specimen placed at this point with the pendulum hanging vertically, the 
pivot-blocks being adjustable. The working resistance to motion is made 
as small as possible. The pendulum itself should rest on knife-edge bear¬ 
ings and should be a heavy flat bar, swinging edgewise, as here shown, to 
reduce the air resistance. The registering apparatus necessarily has some 
resistance, but all these can be evaluated by swinging the pendulum freely 
and noting the loss of energy for a single passage. The potential energy of 
the blow, and the kinetic energy left after breaking the specimen, are found 
as described in Art. 293. 

Mr. Russell has shown that the resilience of cast-iron bars 1 in. by 2 in. 
in cross-section is the same, in inch-pounds per cubic inch of specimen 
lying between supports, whether the test length be 12 in. or 24 in. This 
being the first machine ever designed, so far as the author is aware, which 
could measure the energy absorbed by a specimen when broken by a single 
blow, it becomes extremely interesting to learn how far these tests bear out 
the common assumption that this amount of energy is given by the total 
area of the stress-diagram obtained by plotting simultaneous readings of 
load and deformation in a static test, as fully explained in Art. 53, p. *76 et 
seq. Mr. Russell’s tests indicate, as shown by the following table,* that in 

RESILIENCE BY IMPACT AND BY GRADUAL LOAD. 

Cast-iron bars 1 in. by 2 ins., broken flatwise. 


Lot or Melt Nos. 

Experiment 

Nos. 

By Impact. 

By Gradual Load 

Number of 
Tests Aver¬ 
aged. 

Length be¬ 
tween Sup¬ 
ports, 
in Inches. 

L. 

Resilience in 
Inch-pounds 
per 

Cubic Inch. 

Number of 
Tests Aver¬ 
aged. 

Resilience in 
Inch-pouuds 
per 

Cubic Inch. 

1 . 

125-130 

6 

24 

11.5 

3 

9.0 

2. 

137-139 

3 

24 

10.8 

3 

8.7 

3. 

156-159 

4 

24 

11.4 

3 

8.5 

4. 

219-222 

4 

24 

11.8 

3 

8.8 

6. 

391-393 

3 

12 

17.9 

2f 

11.1 

7 . 

448-449 

2 

12 

14.8 

2f 

8.2 

Averages... i ... 




13.03 


9.05 


I. 




* Trans. Am. Soc. C. E., p. 246. 
f L = 24 ins. with gradual load. 





































IMPACT AND HARDNESS TESTS. 


381 


the case of cast-iron bars 1 in. by 2 in. broken flatwise the energy absorbed 
in the pendulum test is 44$ greater than the energy represented by the 
total area of the stress-diagram in the static test. These results show that 
even after allowance is made for the inertia of the test-bar there is an in¬ 
creased resistance for quick deformations with brittle materials, as was 
shown in Fig. 52, p. 79, for ductile materials. In other words, the real 
resistance to rupture by a single blow is probably always much greater than 
that computed from the total area of the static stress-diagram. 

TESTS FOR HARDNESS. 

295. Hardness Defined. —The term hardness is used in two senses, as 
applied to metals, minerals, and other solids. It is used to signify— 

(a) Resistance to indentation (permanency of form); 

(b) Resistance to abrasion or scratching (permanency of substance).* 

These two kinds of hardness are more or less related, and are often con¬ 
fused. In practice the demands for these two kinds of hardness are quite 
distinct, and hence two very distinct kinds of tests are employed to determine 
them. 

296. Hardness Test for Permanency of Form or Resistance to Indenta¬ 
tion.—The only test of this kind which has ever been standardized is the 
indentation test by means of a pyramidal steel punch, attached to a falling 



Fig. 309.—The Rodman Steel Punch for Hardness Tests. Dimensions in millimeters. 

(Rep. Fr. Com., vol. hi. p. 261.) 

weight. The form most favorable to exact results is that chosen by Lieut.- 
Col. T. J. Rodman (U. S. A.) before 1860,f and shown in Fig. 309 in 
metric measurements. These are used because this test has been standard¬ 
ized in France, and the degree of hardness is given in metric units.J Such 
a steel-point is rigidly attached to the base (or striking side) of the ram in an 
impact-testing machine, such as shown in Fig. 306 or 307 or 308. The sur- 

* After Osmond. 

f See his Report of Experiments on Metals for Cannon and Cannon-powder , 1861. 

\ While the author of this work has, as a rule, expressed quantities in English units 
only, he makes an exception in this case. 



















3S2 


THE MATERIALS OF CONSTRUCTION. 


face of the substance to be tested is planed or filed flat and polished. The 
steel point is then made to fall normally upon the surface from any desired 
height, and the observation consists in noting 

The weight of the ram = W in kilograms; 

The height of the fall = h in millimeters; 

The length of the indentation = l in millimeters. 

The work done upon the body tested, or in producing the indentation, will 
be Wh kilogram-millimeters, provided the anvil, or body struck, was very 
massive and firm in comparison with the iveight of the ram. r Ihis is, of 
course, essential to the correctness of the assumption that the energy of the 
falling body spends itself wholly in producing the indentation; and this must 
be assumed and secured for a perfect accordance of results. 

The volume of displaced material resulting from the indentation will be 
ml 8 , where m will vary with different forms of pyramids, but will be a con¬ 
stant for any one pyramid, or punch. It has been shown most conclusively 
by Lieut.-Col. Martel* that when the essential conditions of the test are 
satisfied, 

For all forms of pyramids, for all weights of ram, and for all heights of 
fall, the volume of the displaced material of a given quality is equal to the 
energy of the blow ( Wh) divided by a constant, D, f which constant is the 
work or energy necessary to displace (by deformation) a unit-volume of that 
material. This constant is therefore characteristic of that material and may 
be taken cts its index of hardness, or of its resistance to indentation. 

Since the kilogram-millimeter units have already been used in France, 
and the hardness of many kinds of materials has been found and published 
on this scale, it would lead to unnecessary confusion to change the units, 
since this would change the numerical index of hardness. 

To find the volume of the pyramidal displacement of the Rodman punch 
(Fig. 309) from the measured length, multiply the cube of the length by 

0.0009413 (log 4.97375), or vol. = 0.0009413/ 3 . 

For any other form of punch the volume would be readily computed, but 
approximately this form is best, because it gives a very large length to be 
measured for a very small volume. In other words, we argue from a longer 
base, thus making the percentage error of observation correspondingly less. 
Furthermore, the indentation is shallow and hence injures the material 
(which may be a finished or unfinished final form) to a less degree. Any 
other form would, however, give strictly comparable results, so that there is 
no real necessity of adopting this particular form. It goes without saying 
that the punch should itself be so hard as not to suffer any permanent de¬ 
formation in service. 


The truth of the theorv that V = 


Wh 


has been established by Martel 


* Commission des Metliodes d’Essai des Materiaux de Construction , vol. hi. p. 261. 
f For durete , hardness. 




IMPACT AND HARDNESS TESTS. 


383 


within the limits of the errors of observation, and hence can be accepted 
v ith confidence, as giving an absolute standard by which to measure hard¬ 
ness when this implies resistance to indentation. The following table con¬ 
tains values of D (degrees of hardness on the Martel scale) in kilogram- 
millimeter units for various metals. 


DEGREES OF HARDNESS ON THE MARTEL SCALE. 


Metals Tested. 


Degree of Hardness. 


Kilogram-millimeter Units.* 


High carbon (“ diamond”) steel, hardened in oil.. 
“ “ “ “ not hardened.... 

Medium steel (for cannons), hardened in oil. 

Hoop-steel (for large guns), hardened in water_ 

Rolled wrought iron. 

Hammered wrought iron.... 

Cast iron (for guns). 

Bronze (cast in shells). 

“ after cold-hammering. 

“ after drawing down 12$ on a mandrel. 

“ cast in sand (C 88, Sn 12, Z 2). 

tl “ “ “ without zinc. . 

Copper, rolled . 

“ reheated and cooled in water. 

Zinc, rolled. 

Tin, cast. 

Lead, cast.. 


613 

460 

455 to 300 

330 to 295 
226 
238 

300 to 208 
154 
238 
310 
137 
115 
156 
64 
77 
33 
9 


297. Hardness Test for Permanency of Substance or Resistance to Abra¬ 
sion. —While a great many tests of this property have been devised and used, 
none of them has given such satisfactory measurable results as the one just 
described for resistance to indentation. The scratch test has long been in use 
for classifying minerals as to their hardness, and ten grades of hardness are 
recognized under this test. It is purely relative, and is entirely inadequate 
to the requirements of the user of metals. By this test the body A is harder 
than B when a point or sharp corner or edge of A will scratch the surface 
of B, and when the converse will not hold. 

Mr. Thomas Turner has devised the instrument shown in Fig. 310, and 
this has been largely used by both Turner and W. J. Keep for the grading 
of cast irons for hardness. In this a diamond point is fixed at the base of 
a vertical pencil which is carried by a perfectly balanced arm. Provision is 
made for loading the pencil by weights (in grams), and the hardness is 
indicated by the number of grams required to make a standard scratch on 
the surface tested. Evidently the standardizing of the scratch offers great 


* To change these figures to pound-inch units, multiply by 1422. 



















384 


THE MATERIALS OF CONSTRUCTION. 


difficulties, so that results obtained by this instrument in the bands of 
different persons would probably not be strictly comparable. 

Prof. Martens (Berlin) has undertaken to standardize this instrument by 
making the load on the pencil a constant and measuring the width of the 



Fig. 310.—Turner’s Apparatus for Testing Hardness. 

scratch with a micrometer-microscope, and this is the method employed by 
the German artillery officers. 

Standard abrasion-machines have also been used (see Fig. 288), but it is 
almost impossible to duplicate the conditions exactly. 

In general, therefore, it may be said that there is now no absolute test 
for hardness as meaning resistance to scratching or abrasion. (For a brief 
account, without illustrations, by Osmond, of the many devices which have 
been tried, see Report of the French Commission , vol. ill. p. 279.) 






























CHAPTER XIX. 


SHEARING AND TORSION TESTS. 

SHEARING TESTS. 

298. Essential Conditions of a Shearing Test. —In order to obtain the 
true shearing strength of any substance it is necessary to develop in it, along 
a given plane, shearing stress only, unaccompanied by the bending stresses of 
tension and compression. To accomplish this it is necessary to concentrate 
the external forces of action and reaction on planes an infinitely small dis¬ 
tance (dx) apart. Any finite distance between these planes will develop a 
cross-bending action and its resultant direct stresses across the plane of 
shear. As it is impossible to so concentrate the external shearing forces, it 
is necessary to overcome the bending stresses set up by the non-concurrence 
of the external forces by preventing the bending of the specimen subjected 
to these forces. This can only be done by reinforcing the specimen between 
the shearing planes. This may be done by grooving the specimen in the 
planes of shear, or by supporting it by auxiliary clamps. As neither of 
these expedients has usually been resorted to in shearing tests, it follows 
that very few such, tests have ever been made in which shearing stress has 
been unaccompanied by large direct stresses.* 

299. The Occurrence of Shearing Stress in Practice. —Shearing stress is 
present in nearly all cases where there is cross-bending (see Art. 37), and in 
rivets, bolts, bridge-pins, crank-pins, etc., shearing stress becomes of practi¬ 
cal interest. In none of these cases, however, is it found acting alone, but 
it is always combined with bending stress. In the case of rivets it is alwavs 
combined with a very great tensile stress, caused by the contraction of the 
rivet in cooling after the heads have been made, this stress from contraction 
in good work always exceeding the tensile stress of the rivet at its elastic 
limit. In fact a riveted joint, if well made, always acts by frictional re¬ 
sistance alone, since this is always more than the working stress on the joint. 
(See a discussion of this subject in Chap. XXVI.) While rivets are computed 
for shear, therefore, as a matter of fact they are seldon subjected to a shear¬ 
ing stress. 

* Both Dr. Kennedy and Mr. Barba grooved their specimens for double shear, and 
also held them in rigid forms. See Rep. French Commission, vol. in, Plate XIX. 

385 



386 


THE MATERIALS OF CONSTRUCTION. 


For these reasons a knowledge of the true shearing strength of any of 
the metals is of little value, except for purely scientific purposes, and for 
computing resistance to torsion, where the stress developed is that of pure 
shear. 

In the case of timber, however, which more often fails in shearing along 
the grain than in any other way, the strength in shearing is of great interest. 

In general the shearing strength of the metals may be taken as 80 per 
cent of the tensile strength. 

300. Shearing-test Appliances. —Shearing tests can be made in an ordi¬ 
nary tension or compression machine, if suitable appliances be used for 
holding the specimen. In Fig. 311 Dr. Kennedy’s appliances for single and 



Fig. 311.—Dr. Kennedy’s Appliances for Single and for Double Shear. 


double shear are shown. For single shear the specimen is held by two half- 
rounds, all enclosed in a cylindrical sleeve. The shearing-faces are rein¬ 
forced by steel rings. The plane of shear thus lies in the line of the axes 
of the two compression shear-blocks. For double shear the specimen is 
grooved on the shearing-planes, and it is also fitted closety into the eyes of 
the steel links through which the forces are applied.* 

In Fig. 312 is shown the shearing-apparatus designed by the author 
for finding the shearing strength of cast iron. Here the specimen is 
gripped firmly at both ends and in the centre, and all bending distortion 
prevented. By preventing this kind of deformation the bending stresses are 
of necessity avoided. The bearing shear-plates at top and bottom are of 
hardened steel. 

For shearing tests on wood the apparatus shown in Fig. 313 has been 
extensively employed by the author. Blocks about 2^ inches square and 8 
inches long are slotted one inch from each end, in planes at right angles to 
each other,’ and also bored at the centre for the fixed hold. A rectangular 
steel pin is inserted in the slot, and the stick is prevented from splitting by 
attaching a clamp with an initial pressure just sufficient to hold it in place. 
The steel pin is pulled by means of bronze stirrups which are held in the 

* This apparatus will not serve for cast iron. See Trans. Inst. Civ. Engrs., vol. xc. 
p. 391. 




























































































































































SHEARING AND TORSION TESTS. 


387 


regular wedge-grips of the testing-machine. After shearing out one end of 
the specimen it is turned over, the lower stirrup revolved 90°, and the other 
end pulled. 



Fig. 312.— The Author’s Shearing-test Apparatus. 

TORSION TESTS. 

301. Contrasted with Shearing Tests. —While torsional stress i.s a pure 

shearing stress (and about the only means of obtaining a pure shearing 
stress), yet a torsion test differs from a shearing test in that the deformation 
acts over any length of bar, taken at pleasure, and in that it is not uniformly 
distributed across the section, but is zero at the centre and increases uni¬ 
formly towards the circumference. This enables the modulus of shearing 
elasticity to be determined by noting the angular distortion over a given 
length of bar, and it also makes possible the obtaining of autographic (or 
plotted) stress-diagrams for shearing stress. The elastic limit and ultimate 
strength in torsion have a value in the designing of shafting of all sorts 
which serve to transmit power. 

302. Torsion-testing Machines. —m Fig. 314 is shown a simple attach¬ 
ment to an ordinary “ universal ’ testing-machine. The power is applied to 
the specimen A by the screw-gear II, and the torsion is resisted by a couple 















388 


THE MATERIALS OF CONSTRUCTION . 


« 



Fig. 313.— Shearing-test Apparatus for Wood. 
































































SHEARING AND TORSION TESTS. 


389 



Fig. 814.—Torsion test Attachment. 



QgCnEP INDICATOR 




t * .*-> r«yp3Sjpn 




Torsion Machine for Short Specimens 









































































































































































































































































































































































































































390 


THE MATERIALS OF CONSTRUCTION. 


one arm of which, G , bears on the weighing-table. The angular deforma¬ 
tion is observed by means of the two collars E and D, the latter holding 
rigidly a bar which moves a pointer over the graduated circle on the former. 



In Fig. 315 is shown a torsion machine for testing large specimens in 
short lengths, while in Fig 31G is shown a large machine for bars of any 
desired length. The former machine is self-contained, while in the latter 































































































































SHEARING AND TORSION TESTS . 


391 



Ftg. 31?.— A 3f-iu. square Bessemer-steel Bar Twisted Hot. (Gassier's Mag., vol. x. p. 

443, 1896.) 










392 


TI1E MATERIALS OF CONSTRUCTION. 


the lifting side of the weighing end is held down to the track by bolts, and 
the downward-bearing end of the couple-arm bears upon a system of weigh- 



Fig. 318.—Tetmajer’s Torsion-testing Machine for Wires, giving Autographic Records. 

ing-levers. it is made in three sizes suited to steel shafts l£ in., 2 in., and 
3| in. in diameter, and for 16 feet in length or less. In this machine the 
specimen is free to contract longitudinally while under test. 



Fig. 319. 


A very perfect machine for testing wires from 0.05 in. to 0.18 in. in 
diameter (No. 18 to No. 7 B. W. G.) and for giving (a) the breaking moment, 
(b) the number of turns, and (e) the complete stress-diagram, is shown in 
Fig. 318.* This machine is used by Prof. Tetmajer and described by him 


* Made by Messrs. Amsler-Laffon & Sons, Schaffhausen, Switzerland 




























































































































































































SHEARING AND T0HS10N TESTS. 


393 


in vol. iv. of his Communications. The specimen is kept in tension 
during the test by a weight suspended by a cord connected to the carriage 
at the resisting (and recording) end of the specimen. The resisting moment 
is developed by means of two weights suspended by cords which run in 
symmetrically arranged spiral grooves. 

A simple machine without recording apparatus is shown in Fig. 319. 


CHAPTER XX. 


COLD-BENDING AND DRIFTING TESTS. 

COLD-BENDING TESTS. 

303. Their Character and Significance. —The test of the ductility of a 

malleable metal by bending it cold is the most common and perhaps the most 
useful of all the tests which can be applied to it. For wrought iron and 
structural steel this test approaches more nearly to the severe usages of actual 
practice than does the tension test with its elastic limit, ultimate strength, 
elongation, and reduction of area. It is not so easily standardized, however, 
.and it is employed less in America than in Europe, partly because no stand¬ 
ard methods and results have been agreed upon here. If a sample of wrought 
iron or steel will, when cold, fold upon itself absolutely, as shown in Figs. 



Fig 320.—Cold-bemling Test of a 51-lb. 15-in. Steel Channel-bar. Thickness of 

web = 0.78 in. ( Engr. News , vol. xxxiu. p. 272.) 

320 and 322, or make the double fold as shown in Fig. 321, there can be 
no doubt of its high quality. When it fractures, however, at intermediate 
stages of this process, the question of its quality is left in doubt, and some 
standard limit is required if this test is to be made the basis of acceptance. 
The great advantage of this test is that it can be made at any time in the 
shop, without the expense attaching to tension tests, and by the man who 
uses or makes up the material. No standard method of making this test, 
therefore, should remove it beyond the range of ordinary shop appliances. 
.In Europe a number of special machines are in use for making these tests, 

394 








GOLD-BENDING AND DRIFTING TESTS. 


395 


but only shop-tools will here be assumed as available. With these methods, 
and in the hands of the same operator, uniform and comparable results may 
be obtained. 

304. Methods of Making Cold-bending Tests. —If the specimen is not 
too large, a strong vise may be employed. If the bend is to be a true fold 
(radius of curvature = 0), the specimen should be bent about the sharp edge 
of the vise. If it is to be bent to a given radius, an auxiliary plate, dressed 
to this radius, must be clamped with the specimen in the vise. In either 



Fig. 321.—Double Cold Bends on f-in. Steel Plates. (Eng. News, vol. xxxm. p. 272.) 

case the specimen must he clamped fast to a long steel bar , or lever , so as to 
prevent all bending beyond the curved section. For this purpose two clamps * 
are required, one of which must be close down to the vise. The specimen 
is then bent to 90° by hand. Striking the specimen with a hammer should 
be avoided, as this kind of action cannot be standardized. If the specimen 
is to be folded flat upon itself, it may be removed from the vise after it has 
been bent to a right angle, and a second bar clamped to the other leg, and 
these two bars can now be drawn together by hand. The final closing down 
of the specimen may be done in a vise or under the hammer,—a steam- 
hammer always preferred. 

The French Commission have adopted the interior angle as the index of 
the ductility. Thus if a straight bar bends through an angle of 60° before 
rupture, it leaves an angle of 120°, and this is the angle of record. A record 
of 0° signifies that the bar has bent through 180°, and that it has been 
either closed down flat or bent to a given radius, according as the radius of 
the bend is given as zero or something greater. 

* Specially devised stirrups or clevises should be made up for clamping the specimens 
to the bending bar. 






396 


THE MATERIALS OF CONSTRUCTION. 


If the specimen is too large to bend by band as described above, it may 
be bent under a steam-hammer (or in a hydraulic or screw press, or in a test¬ 
ing-machine, or even by a heavy sledge), by resting it on supports as a 
beam and striking it at the centre. After bending it in this way through an 



Fig. 322.—Soft Bessemer-steel Bars, 3 in. by 2 in. in cross-section, Bent Cold. ( Cassier’s 
' Mag., vol. x. p. 442, 1896.) 

angle of about 60°, it may be set on end and struck by the hammer (or placed 
in a press or testing-machine), as a bent column, and so brought down to 
any desired angle or radius of curvature. This required radius of curvature 
will have to be reached hv flattening down the bent bar, after the zero angle 










COLD-BENDING AND DRIFTING TESTS. 


397 


(180° of curvature) lias been attained. The ideal appliance here is a press 
of some sort, but this requires a special machine (perhaps an ordinary “ bull¬ 
dozer,” used for straightening, or curving members, might serve), and in the 
absence of these a steam-hammer answers very well. A sledge is not good, 
as it is too light and requires blows having too high a velocity, which spend 
their energy in deforming the specimen at the point of impact and may 
produce its rupture earlier than the other methods would. 

Prof. Tetmajer has a machine for making bending tests without the use 
of a mandrel, and whereby a uniform bending action is given to the bar. 
This develops the distributed elongation of the specimen, whereas a bend 
concentrated at one point develops the “ reduction of area ” quality. Thus 
a high-grade steel wire which will not elongate over two or three per cent 
may, on failure in tension, show a reduction of area of GO per cent. Such 
a wire would fold over to a much sharper curve (smaller radius) than it 
could be bent to through a full circle. 

Preparation of the Specimen .—If the specimen has been cut from a 
plate or from a structural form, and it is to be tested in comparison with or 
on the same basis as rolled bars, either round or rectangular, then the 
sheared edges should be removed by planing or filing where the bending is 
to be effected, in order to remove the brittle material resulting from the 
shearing action. 

On the other hand, if it is desired to learn the action of the metal after 
it has been punched or sheared or threaded, then the specimen is purposely 
so prepared and tested without removing these hardened and serrated sur¬ 
faces. The cold-bending test of such prepared specimens develops the 
injurious effects of these shop processes (punching, shearing, and threading) 
as nothing else can, and it is therefore necessary to use it for such purposes. 

The French Commission have recommended a length of 10 inches and a 
width (of plate specimens) of 1.6 inches, the thickness to be that of the plate 
or bar. 

Sometimes specimens are nicked or grooved on one side and then broken 
in cross-bending, under the hammer, to test relative brittleness. This is 
not a test that can be relied on to give absolute results, but Prof. Tetmajer 
used it to good effect to disprove the commonly accepted theory that even 
low steel is more brittle than wrought iron when subjected to shocks. 
Photographic views of the results of these tests are shown in Fig. 323. The 
depths of these specimens are shown in the figure. The six upper ones were 
0.8 inch thick, and the four lower ones 1.2 inches thick. The tension tests 
on these specimens gave the following average results (eighteen tests on 
each material): 


Material. 

Modulus of 
Elasticity. 

True Elastic 
Limit. 

Apparent 
Elastic Limit. 

Ultimate 

Strength. 

Per cent 
of Elon¬ 
gation. 

Reduc¬ 
tion of 
Area. 

Low steel. 

"Wrought iron .. 

Lbs. per sq. in. 
31.000,000 
28,600,000 

Lbs. per sq. in. 

28,500 

21,800 

Lbs. per sq. in. 

36,600 

33,000 

Lbs. per sq. in. 
61,000 
52,200 

% in 8 

27.8 

16.0 

% 

59.3 

21.4 
























398 


THE MATERIALS OF CONSTRUCTION. 



Fig. 323.—Showing Relative Resistance to Shock of Wrought-iron and Basic Bessemer-steel Bars -which 
had been Grooved on the Tension Side to a depth of 0.06 in. (Tetmajer, vol. iv. PI. X.) W = 
wrought iron, S = steel. The hammer weighed 660 lbs. and fell 9 in., 19 in., 29 in., 51 in., and 79 
in. for the five sizes respectively, the span being always 40 in. The number of blows were 2, 3, 2, 
2, 1, 4, 1, 7, 1, and 6 for the ten specimens as shown above, respectively. 

All the bars were furnished by the well-known works of Wendell & Co., Hayauge, Lorraine. The 
chemical composition of the two metals was as follows : 

C Si PS Mn 

Wrought iron .05 to .06 .05 to .15 .30 to .50 .02 to .04 trace 

Steel.08 to .12 trace .03 to .06 .02 to .04 .40 to .70 

[The high percentage of phosphorus in the wrought iron was due to the slag.] 



















This plate illustrates the relative resistance to impact of wrought iron and steel when made up into plate girders. These tests were made by 
Prof. Tetmajer. and the results are given in vol. iv. of his Communications. These girders were 20 in. high and rested on supports 6 ft. apart. 
Nos. 4070 and 4672 were of wrought iron, and Nos. 4671 and 4673 were of mild (60,000-lb.) steel. All of them were subjected to five blows of a rani 
weighing 2200 lbs., falling 4, 8, 12, 16, and 16 feet, respectively. \t 0 face p. 398.J 


































GOLD-BENDINO AND DRIFTING TESTS. 399 

The great superiority of the steel in the impact tests is evident from the 
figure. 

In the cold-bending tests on the same forms, flatwise, the steel specimens 
0.8 inch thick folded flat without sign of rupture, while those 1.2 inches 
thick cracked in flattening down. The wrought-iron specimens 0.8 inch 
thick cracked after bending through an angle of 120°, and the 1.2-inch 
specimens after bending through an angle of 60°. 

305. Comparison of Results of Cold-bending Tests with the Tensile 
Strength and the Percentage of Elongation. —In Bacle’s report on Various 
Cold Tests of Materials, in the French Commission Report, vol. in. p. 311, 
are given the mean results of several thousand tests in tension and cold bend¬ 
ing on wrought iron and soft steel, received from many different sources, 
made by M. Hallopeau, a member of that Commission, and given in the fol¬ 
lowing tables. These results are not only of great value for the information 
itself, but they will serve to enable one to prepare standard specifications for 
cold-bending tests from the relation of the results of these to the results of 
tension tests which have long been the standard tests of acceptance in this 
country. 

TABLE XVIII.-RELATIVE RESULTS OF TEXSIOX AND COLD-BEXDING TESTS. 


Material. 

Tension Test. 

Bending Test. 

Elastic Limit. 

Ultimate 

Strength. 

Elonga¬ 

tion. 

Cracked 
at Angle 
of 

Ruptured 
at Angle 
of 

Wrought iron, with grain. 

“ “ across “ . 

Low steel (57,000 to 60,000 T. S.) 

Medium steel (64,000 T. S.). 

High steel (68,500 to 71,500 T. S.) 

Lbs. per sq. in. 

32,000 

30,000 

29.500 
34,000 

35.500 

Lbs. ppr sq. in. 

48,500 

42,000 

60,000 

65,000 

72,000 

Percentage 

14.0 

6.5 

27.0 

25.0 

24.0 

Degrees. 

80 

130 

0 

0 

0 

Degrees. 

30 

115 

0 

0 

0 


The tension-test bars were 4 in. long, 1.6 in. wide, and 0.4 in. thick. 

The bending-test bars were 6 iu. “ 1.6 in. “ “ 0.4 in. “ 

The bending-test angle of record is the angle formed by the two ends of the bar after 
bending, or it is the supplement of the angle through which bending has taken place. 

It will be seen from the above table that while the bending test would 
•serve to distinguish varying qualities of wrought iron, it would not serve to 
distinguish these three grades of steel, since they all bent through 180° and 
folded flat without even cracking. Since these grades require distinction in 
practice because of the different degrees of injury produced on them by 
punching, the specimens can be punched and then bent, and the shades of 
hardness indicated by the greater angles at which cracks appear. This has 
been done by M. Hallopeau, and the results are shown in Table XIX. The 
plates were all the same size as those given in the previous table, the punched 
and drilled holes being 0.8 inch in diameter, or one half the width of the 
bar, the thickness being 0.4 inch. The die side of the plates was made the 
tension, or convex, side. 



















400 


THE MATERIALS OF CONSTRUCTION. 


TABLE XIX.—EFFECTS OF PUNCHING AND DRILLING ON WROUGHT IRON 
AND STEEL, AS DETERMINED BY TENSION AND COLD-BENDING TESTS 
ON BARS 0.4 INCH THICK. 


Material. 


WROUGHT IRON. 
Plain. 


Natural i With the S rain . 

iNatuiai \ Across the grain. 

Annealed \ f iUl ‘ S rai “.. 

\ Across the grain. 

Hardened in water] ^ith U ‘f S rai “.. 

( Across the grain. 

Hardened and annealed \ • 

l Across the grain. 

Punched. 


Natural \ f ith ih * S rain . 

Across the grain. 

j With the grain. 

( Across the grain. 

in water i \ VU1 ‘ ,h e S rain .. 

Across the grain. . .. 

and annealed] tb “ Srain... 

( Across the grain. 
Drilled. 


Annealed 

Hardened 

Hardened 


Natural ^ 
Annealed 
Hardened 
Hardened 


( With the grain. 

'( Across the grain. 

^ With the grain. 

} Across the grain. 

With the grain. ., 
Across the grain. 

and annealed 1 ^itl. the grain. 


in water 


( Across the grain 


LOW STEEL. 
Plain. 

Natural. 

Annealed. 

Hardened in water. 

Hardened and annealed. 


Punched. 

Natural. 

Annealed. 

Hardened in water. 

Hardened and annealed... 


Drilled. 

Natural. 

Annealed. . . .'. 

Hardened in water. 

Hardened and annealed.. 


Tension Test. 

Bending Test. 

Elastic 

Limit. 

Ultimate 

Strength. 

Elonga¬ 

tion. 

Cracked 
at An¬ 
gle of 

Rupt’d 
at Angle 
of 

Lbs. 

per sq. in. 

Lbs. 

per sq. in. 

Percent¬ 

age. 

Degrees. 

Degrees.. 

32,000 

48,500 

14.0 

80 

30 

30,000 

42,000 

6.5 

130 

115 

20,000 

47,000 

19.8 

65 

20 

26,500 

41,000' 

8.3 

115 

85 

33,500 

53,000 

15.0 

80 

40 

39,000 

46.000 

3.3 

135 

100 

28,500 

47,000 

16.7 

100 

50 

28,500 

41,500 

7.7 

105 

80 

29,000 

38,500 

1.0 

175 

150 

26,000 

32,000 

1.0 

180 

175 

42,000 

46,000 

2.4 

170 

150 

29,000 

34,000 

1.0 

175 

165 

• • • t 

56,000 

# , 

175 

160 

33,500 

38,000 

1.0 

178 

175 

.... 

43,500 


170 

150 

29,500 

37,500 

1.5 

175 

165 

28,500 

42,000 

2.7 

172 

165 

25.000 

36,000 

1.5 

177 

172 

29,000 

44.500 

3.3 

176 

172 

24,500 

33,000 

1.8 

177 

173 

36,500 

54,000 

1.8 

175 

168 

30,000 

44,000 

0.8 

177 

173. 

29,500 

41,000 

3.2 

172 

165 

27,000 

35,000 

1.5 

178 

175 

29,500 

60,500 

27.0 

• • 

• • 

28.500 

59,000 

27.8 

• • 

• • 

34,000 

65.500 

22.4 

• • 

# # 

29,000 

59,000 

30.0 

• • 

• 

36.200 

60,000 

4.5 

100 

60 

36,500 

55,000 

4.6 

90 

59 

45,000 

67,500 

4.1 

150 

135 

36,400 

58,000 

5.0 

90 

60 

36,000 

60,200 

6.8 

45 

10 

34,200 

59,700 

7.4 

40 

5 

39,200 

67,000 

6 8 

110 

100 

33,500 

59,700 

7.1 

20 

10 


















































GOLD-BENDING AND DRIFTING TESTS. 


401 


EFFECTS OF PUNCHING AND DRILLING ON WROUGHT IRON AND 

steel— continued. 


Material. 


MEDIUM STEEL. 
Plain. 

Natural. 

Annealed. 

Hardened in water. 

Hardened and auuealed. 

Punched. 

Natural. 

Annealed. 

Hardened in water. 

Hardened and annealed. 

Drilled. 

Natural. 

Annealed. 

Hardened in water. 

Hardened and annealed. 

HIGH STEEL. 
Plain. 

Natural. 

Annealed. 

Hardened in water. 

Hardened and annealed. 

Punched. 

Natural. 

Annealed. 

Hardened in water.. 

Hardened and annealed. 

Drilled. 

Natural. 

Annealed. 

Hardened iu water. 

Hardened and annealed. 


Tension Test. j Bending Test. 


Elastic 

Limit. 

Ultimate 

Strength. 

Elonga¬ 

tion. 

Cracked 
at An¬ 
gle of 

Rupt’d 
at Angle 

of 

Lbs. 

per sq. in. 

Lbs. 

per sq. in. 

Percent-i 
age. 

Degrees. 

Degrees. 

34,000 

65,500 

25.0 

• • 

• • 

32,800 

64,000 

26.8 

• • 

• • 

37,000 

73,500 

23.8 

• • 

• • 

33,800 

66,000 

26.0 

• • 

• • 

36,500 

67,000 

4.5 

100 

80 

35,500 

64,000 

4.7 

95 

75 

51,000 

77,000 

2.2 

145 

130 

37,000 

64,500 

4.7 

100 

75 

36,500 

66,000 

6.2 

70 

50 

35,500 

64,500 

6.5 

65 

40 

51,000 

73,000 

6.3 

100 

80 

36,000 

65,000 

6.5 

60 

40 

35,500 

72,000 

24.0 

• • 

• • 

36,200 

70,000 

25.0 

• • 

• • 

43,500 

80,000 

20.0 

20 to 60 

• • 

35,500 

71,300 

25.0 

• • 


47,000 

72,000 

3.9 

140 

105 

47,500 

71,000 

3.4 

120 

95 

71,000 

80,000 

3.4 

160 

145 

47,000 

71.000 

3.4 

135 

105 

39,700 

71,800 

5.5 

80 

60 

38,600 

69,000 

5.6 

70 

55 

56,700 

82,000 

5.8 

140 

125 

39,000 

71,600 

5.7 

85 

60 


Note. —All the bars were 1.6 in. wide and J0.4 in. thick. The elongation in the 
tension test was measured on a length of 4 in. with both the plain and the punched or 
drilled specimens. In the former case this elongation occurred throughout this entire 
distance (4 in.), while in the latter it occurred only in the vicinity of the hole, but was 
credited to the entire distance of 4 inches in computing the percentage of elongation. 
These percentages are therefore not comparable as showing loss of ductility (as has been 
Assumed in the Rep. French Com.). 

The bending-test angle of record is the angle formed by the two ends of the bar after 
bending. 


























































402 


TEE MATERIALS OF CONSTRUCTION. 


The following conclusions may be drawn from Table XIX: 

1. The reduced ductility of wrought iron across the grain is fully brought 
out both in the elongation of the tension tests and in the angles of rupture 
in the cold-bending tests. 

2. The weakening effect of both punching and drilling is very much 
greater with the wrought iron than with the soft and mild steels, and some¬ 
what greater than it is on the medium steel. 

3. The annealing of the punched specimens in no case appreciably 
increased their ductility, as shown by both the tension and the bending 
tests. It increased the strength of the wrought-irou specimens somewhat, 
but it lowered the strength of the steel specimens. 

4. The drilled specimens of wrought iron do not differ apjjreciably from 
the punched either in strength or ductility, while with the steel of all 
grades the ductility of the drilled specimens is far greater than that of the 
punched specimens, although the ultimate strength is the same. 

5. The change from 65,000- to 72,000«lb. steel is very clearly indicated 
by the bending test, where in the punched specimen, “natural,” the angle 
through which the specimen bent before cracking is 100$ greater with the 
former than with the latter. No such difference aj^pears as between the 
60,000-lb. and the 65,000-lb. steel, showing that they are about equally well 
adapted to such work. In the “ plain 99 specimens all three grades of steel 
closed down entire (angle = 0) without sign of failure, thus manifesting no 
difference in hardness. The bending test on punched specimens, therefore, 
develops clearly this difference in fitness for riveted construction, and it 
might well be used as a shop-criterion of acceptance. Thus the 60,000-lb. 
and the 65,000-lb. steels bent through an angle of 80° after punching before 
a crack appeared, while the 72,000-lb. steel bent through an angle of only 
40° before cracking. If an angle of 60° were specified on this test for plates 
0.4 in. thick (leaving an angle of 120° formed by the two ends of the bar) 
before a crack should appear, it would seem to rule out the higher carbon- 
steels, which are injured by punching and shearing. This angle would be 
different, however, for different thicknesses of plate. 

306. Combined Specified Requirements in Tension and Cold Bending.— 
The combined requirements given in Table XX are reproduced from the' 
Report of the French Commission, vol. hi. pp. 342-353. While the joint 
requirements of many French government bureaus are there given, only 
those of the Artillerie de terre are here given. 

The Committee of the American Society of Civil Engineers has recom¬ 
mended (1896) the following cold-bending tests of plain specimens: 

Wrought-iron specimens should bend through 90° without fracture, with inner 
radius not exceeding twice the thickness of the test specimen for bar-iron nor three 
times that thickness for plate and shape iron. 

Rivet-iron and Rivet-steel bars, when heated to a low cherry-red and quenched 
in water (this for the steel bars only), must bend through 180° to a close contact 
(radius = 0) without sign of fracture. 


COLD-BENDING AND DRIFTING TESTS. 


403 


Low Steel (GO,000 lbs. T. S.), when treated in the same manner, must bend to a 
zero angle (through 180°), with au inner radius equal to the thickness of the speci¬ 
men, without sign of fracture. 

Medium Steel (65,000 lbs. T. S.) specimens, cut from bars, plates, or structural 
forms, in their natural state, must bend through 180°, with an inner radius equal to-- 
one and one-half times the thickness of the specimen, without sign of fracture. 

High Steel (70,000 lbs. T. S.) specimens, cut from plates and forms, in their natu¬ 
ral state, must bend through 180° to an inner radius equal to twice the thickness of 
the specimen without showing sign of fracture. 


TABLE XX.—COMBINED REQUIREMENTS IN TENSION AND COLD BENDING. 


Material. 

Tension. 

Thick¬ 

ness 

Cold Bending. 

Ultimate 

Strength. 

Elonga¬ 

tion. 

of 

Speci¬ 

men. 

t 

Angle 

before 

Cracking. 

Radius 
of Bend. 

WROUGHT IRON. 

Rolled Forms (Round and 
Rectangular). 

First-class charcoal iron, threaded 1 
First-class puddled iron, threaded 
Good “ “ plain.... 

Common “ “ “. 

Iron for bolts, threaded . 

Lbs. per sq. in. 

48,500 

48,500 

• • » ' 

48*500 

Per cent. 

25 

25 

• • • • 

• • • • 

25 

In inches 

t < 1.6 
t < 1.6 
t < 1.6 4 

t < 0.6 

Degrees. 

0* 

0 3 

0 

90 

0 

0.51 

0.5 1 

1.5 to 2.0* 
2t 

0 5 1 

(i if if a 

* ^ 0.6 

90 

0.51 

Plate Iron . 6 

WITH THE GRAIN. 

First-el ass charcoal iron.. 



t < 0.4 

0 

0 

Refined puddled iron. 

50,000 

io 

t < 0.4 

0 

0 to 1.5£ 

ACROSS THE GRAIN. 

First-class charcoal iron . 

t < 0.2 

0 

0 

i < H U 



y > 0.2 

1 < 0.4 
t < .08 

i 90 

0 

Refined puddled iron ... . 

50,000 

10 

f 

0 

0 

(( <( a 

y > .08 

1 < 0.2 
y> 0.2 

1 < 0.4 

any t 
any t 

t < 0.2 

£ 0 

1.5* 

n n a 



f 

i 90 

t 

STRUCTURAL STEEL. 

Low and Medium. 

Rolled forms hardened . 

48,000 to 60,000 
48,000 to 64,000 

57,000 to 68,500 

26 

) 

0 

0 

Plates. 5 “ . 

23 to 25 

0 

0 

High Steel. 

Rolled forms, hardened .. .. 

22 

0 

0 

a a a 


t > 0.2 

0 


Plates 5 1 * . 

60,000 to 71,000 
57 000 to 68 500 

21 

\t < 0.2 

0 

0 

a *« 

21 to 23 

t> 0.2 

1 

0 

t 






1. Screw-threads cut on bar where the bending occurs, as shown in Fig. 324. 

2. This is the angle formed by the two ends of the bar after bending. 

3. Some cracks are allowed here at the bottoms of the threads. 

4. When the iron has a greater thickness than 1.6 in. it is to be cut down to this 
thickness. 

5. Specimens sheared off and tiled up smooth. 

307. Comparison of Tension, Impact, and Cold-bending Tests.— It will be 
seen from the following tables that the loss of ductility in punching iron 












































404 


THE MATERIALS OF CONSTRUCTION. 


and steel plates, and the benefit of subsequent annealing, are best developed 
by impact tests. Also, the benefits of enlarging punched holes by boring 
and reaming. The tables are compiled from M. IfallopeaiTs experiments 
described above, and are given in Rep. Fr. Corn., pp. 356-7. 

These test-bars were 8 in. long, 2.4 in. wide, and 0.32 in. thick. The 
punched and drilled holes were 0.8 in. in diameter, or one third the width 
of the plates. The hammer used in the impact test weighed 88 lbs., and it 
had a constant fall of 16 in. The average sums of all the heights of fall 
before cracks appeared are given in the table. The figures given are the 
average results of many tests. 


TABLE XXI.—COMPARISON OF RESULTS BY TENSION, IMPACT, AND COLD¬ 
BENDING TESTS ON PUNCHED AND DRILLED PLATES. 


Material. 


Wrought iron, natural.. 
“ “ annealed 

Steel, natural. 

“ annealed. 


Tension Tests 


Impact Tests. 


Oil 


Total Height of 

the Plain Specimens. 


Drops. 






Holes Punched. 


A 







"So 




0.04 in. 


u 


73 


small.* 

S 

IQ 

B 

V 




ft 

o 

<D 

a 

o 

<3 

ft 

6 

N 


<D 

C/2 

a 

bC 

a 

VI 

<D 

55 

<D ^ 

C 

S p 

a 


o 

c 

"G 

c O 

go 

w 

p 

W 

x 

fa 

M 

« 

lbs. sq. in. 

lbs. sq. in 

% 

in. 

in. 

in. 

in 

39,000 

55,000 

14.0 

32 

16 

27 

32 

• • • • 

• • • • 

• „ . 

37 

37 

43 

37 

43,500 

59,500 

29.5 

108 

62 

85 

77 

... 

• • • • 

.... 

130 

107 

128 

112 


Cold-bending Tests. 
Angles when 
Cracks appeal ed. 


Holes Punched. 




0.04 

in. 



small. 

jD 




‘E 

ft 

<D 

N 


73 

c n 

CO 

'C ? 


(D 


X 13 

G 3 

o 

p 

U — 

CO 

go 

X 


m 

« 

deg. 

des\ 

deg 

deg. 

173 

177 

174 

174 

173 

173 

172 

173 

164 

168 

165 

166 

159 

161 

160 

161 


* This is too small an enlargement to remove the material injured by punching, and 
hence these results do not fully develop the differences of treatment.— J. B. J. 


TABLE XXII.—COMPARISON OF RESULTS OF THE IMPACT TESTS. 


Relative Treatment of Specimens. 

Wrought Iron. 

Steel. 

73* 

*3 

X 

B 

B 

73 

x 

£ x 
gi a 

B 

*g73 

C X 

V. ~ 
cc aj 

X X 

x a 

K B 

W ■< 

73 

X 

*5 

X 

B 

B 

<< 

73* 

X 

© f 

X % 

B 

C X 

v. aS 

X X 

X B 

X s 

H <! 

Drilled full size.... 

Punched 0.04 in.* small and drilled out. 

Punched 0.04 in.* small and reamed out..... 
Punched full size. 

inches. 

37 

43 

37 

37 

inches 

32 

27 

32 

16 

% 

14 

59 

14 

130 

inches. 

130 

128 

112 

107 

inches. 

108 

85 

77 

62 

% 

20 

50 

45 

72 

Superiority of drilling over punching. 

Benefit of enlargement by drilling. 

“ “ “ “ reaming. 

% 

0 

16 

0 

% 

100 

69 

100 

t • • • 

• • • • 

• • • • 

* 

21 

20 

5 

% 

74 

37 

24 



* See note following Table XXI. 



















































































COLD-BENDING AND DRIFTING TESTS . 


405 


The following are some of the more important conclusions to be drawn 
from Tables XXI and XXII: 

1. The great superiority under impact of the steel over the wrought-iron, 
with all kinds of treatment. 




Tig. 324.—Cold-bending Tests of Best Wrought-iron, 1 in. to 2 in. in diameter. (From 

Rep. U. S. Test Board , 1881, vol. i.) 

2. The excess in strength of the annealed over the unannealed speci¬ 
mens in all cases, with both iron and steel. 



















406 


THE MATERIALS OF CONSTRUCTION. 


3. The superiority of drilling over punching in all cases, this being 100$ 
with the wrought-iron and 74$ with the steel plates, under the impact tests. 

4. The great benefits of enlargement of punched holes by drilling or 
reaming, this being an average of 85$ with the wrought-iron and 30$ with 
the steel plates, when the thickness of plates was 0.32 in. and the enlarge¬ 
ment only 0.04 in 

With greater thicknesses of plate the superiority of steel over iron would 
probably be somewhat less, while the differences indicated in 2, 3, and 4 
would be greatly increased. With a greater enlargement of punched holes, 
also, the benefits of reaming would be much more marked, especially on the 
steel plates. 

DRIFTING TESTS. 


308. Their Character and Significance.— These, like the cold-bending 
tests, are such as may be applied in the workshop and by the workmen 

themselves with their ordinary shop appli¬ 
ances. The test consists in punching or 
Jporing holes of given diameters (varied with 
the thickness of the plate) at given distances 
from the edge of the plate or structural 
form, and then enlarging it by driving in it 
a drift-pin, as shown in Fig. 325, the per¬ 
centage of enlargement without cracking- 

o O O 

being a very good indication of the ductility 
of the metal. To serve as a criterion of 
comparison, however, it must be reduced to 
fixed rules, the same as all other kinds of 
tests. 

A specification commonly used in France 
is as follows:* 



Fig. 325.—Drifting Test on -f^-in. 

j| in. Hole 
in Diameter. 


Steel Angle. A 
Drifted to 2 T 5 g in. 


Wrought-iron bars shall be cut both with and 
across the grain, 3 in. wide, and three holes 
punched, f in. in diameter and 2f in. apart, along 
the central line of the plate. These holes shall then 
be enlarged, beginning with the central one, and 
using a drift-pin which increases its diameter at 
the rate of 1 in 10. Plates 0.20 in. thick should 
submit to an enlargement of the f in. hole to a 
diameter of 1 in.; plates 0.25 in. thick should 
enlarge to 1.2 in. diameter; plates 0.30 in. thick 
should enlarge to 1.32 in. diameter; and plates 


( Engr . News, vol. xxxm. p 
272.) 

thicker than 0.32 in. should enlarge to from 1 in. to 1.3 in., according to quality, 
without showing any sign of failure. 

Steel plates, similarly prepared, of 57.000 lbs. tensile strength should enlarge to 
1.6 in. diameter after annealing and to 1.5 in. diameter after hardening in water. 
Steel plates of 57,000 to 04.000 lbs. tensile strength should allow a fin. hole to 
enlarge to 1.5 in. diameter after annealing and to 1.4 in. diameter after hardening 
in water. 


* That of the Eastern Railway Company. 







CHAPTER XXI. 


THE TESTING OF CEMENT. 

309. The Standard Scientific Tests of Cement are those which are made 
to determine the following properties: 

(n) Strength, neat and with different proportions of sand; 

(b) Fineness of grinding; 

( c ) The thoroughness of the burning; 

( d ) The rate of setting; 

(e) The permanency of volume, commonly called the test for “ sound¬ 

ness.” 

The strength of cement and of cement-mortar is usually determined 
by the tensile test on small shapes, called briquettes, which have hardened 
under water for varying periods of time. The more common periods are: 
for natural cement, one day and seven days; for Portland cement, seven days 
and twenty-eight days. It is well, however, to extend the time of setting to 
a longer period if practicable. Since natural cement usually sets and 
hardens more rapidly than Portland cement, it is sometimes used in place of 
the Portland, where but a short period of time can be allowed for the test¬ 
ing. Thus for street improvements the material is usually tested after it is 
brought upon the works, that is to say, placed upon the sidewalks; and as it 
here forms a serious obstruction, it is desirable to have the tests made in as 
short a time as possible. Since the one-day test for a quick-setting natural 
cement will indicate its quality, such a material is often used, solely on this 
account. 

Although cement is more commonly subjected to compression, yet it has 
been found that the tensile test effectually indicates the compressive strength 
(see Fig. 337). This holds true both for the neat cement and for cement- 
mortars. 

Since cement is always used mixed with sand, some of the highest authori¬ 
ties are now advocating the abandonment of the neat-cement tests for 
strength and making the strength test on a mortar containing three of sand 
to one of cement, by weight, in the case of Portland cement, and two of 
sand to one of natural cement, by weight, these being the usual proportions. 
For special purposes four or five parts of sand may also be employed, 


408 


TEE MATERIALS OF CONSTRUCTION. 


especially with finely-ground cements, or such as give a residue of Jess than 
10 per cent on a sieve having 14,400 meshes per square inch (2300 per square 
centimeter). Since in the sand mixtures a standard sand must be employed, 
it has become customary to use clean, sharps and which has passed a No. 20 
sieve (20 meslies per linear inch), and stopped on a No. 30 sieve (30 meshes 
per linear inch). In order to further insure identity of the sand used, the 
American Society of Civil Engineers, has recommended that crushed quartz 
be used, such as is employed in the making of sandpaper. The author does 
not favor this practice. This material has fully 50 per cent of voids, while 
the ordinary sands, with roughly rounded grains, contain but about 33 per 
cent of voids. Any good, sharp, clean sand, therefore, of the size 20-30 
should give very nearly uniform results which will average much higher 
than those obtained with crushed quartz, unless the quartz briquettes be 
thoroughly compacted by hard hammering. 

All tensile-test briquettes of Portland cement (neat or with sand) should 
be kept in a moist atmosphere for 24 hours, and then kept the remainder of 
the period under water. Natural cements are kept from one to four hours 
in air (or till they have set) and then put in water. 

The importance of maintaining the water for mixing, and for the bath 
during the entire hardening period, at a standard temperature, in order to 



Fig. 326.— Effect of Temperature of Cement on Time of Setting. (Wheeler, Rep. Clif. 

Engrs., 1895, p. 2936.) 


obtain uniform results, is clearly shown by Figs. 326 and 327. In the 
former it is shown that the time of setting is greatly shortened by increasing 
the temperature of the mixing water, while Fig. 327 indicates that the 
strength attained in a given time may be greatly increased by raising the 
temperature of the bath from 40° to 80° F. In the case of normal mortar, 
1C. :3S., this increase, at two months, was from 100 lbs. to 230 lbs. per 
square inch. The Fifth International Convention for Unifying the Methods. 






















TESTING OF CEMENT. 


409 ' 


of Testing Materials (Zurich, Sept. 1895) decided that it was not advisable' 
to hasten the hardening process by raising the temperature of the bath, 
since, after numerous trials, uniform results could not be obtained. 




<000 






T“ 

§ 



.if 

\\S ^ 

f"'* 

v--'-'-'- 

__ 

_ 



w 

rn 






T]:0‘ 

if 


>-- - 


y-~ _ 

~ 

__ —- —4 ) 



Ps 

_ Aj 


nS 


3 20 


^ --- 

- < 

r7 nA V. 

)— Sy. 

0 

CAT / 

— 

— 

s' 

S' 

r 


y'- - 




^ /;/ 

A-- 

-/LTA 

V / 7 

F 77 

A TO 

' F £ 




TOT SO SO 70 SO<7: 

Fig. 327.—Showing Effect of Temperature of Immersing Tanks on the Rate of Harden¬ 
ing of Natural Cement-mortar. (Wheeler, Rep. Chf. Engrs., 1894.) 


310. The Fineness of the Grinding is determined by passing the cement, 
through sieves of a specified number of meshes to the lineal inch. While. 


/V 













t?# 

M 

% 

§ 




& 


~~s 


& 


1 


•1 




\ § 


1 




Vs 


-1 

70S 


§ 






1 

% 


1 











Fig. 328._Showing Absence of Cementing Properties of the Coarser Particles of 

Cement, 1 C. : 3 S., age 4 mos. (Jour. Assoc. Eng. Socs., vol. xiv. p. 245.) 


the size of such meshes would of course depend on the diameter of the 
wire used, it is difficult to determine this diameter, while the counting of 





































410 


THE MATERIALS OF CONSTRUCTION. 


the meshes is practicable. It has been found by experiment, Fig. 328, that 
only the finest or most impalpable dust is really active in the setting and 
hardening of the cement, the coarser grains acting as so much inert matter, 
which might as well be replaced by sand. The proportion of the cement 
which passes a sieve of less than about 100 meshes to the lineal inch does 
not give any intelligent idea of the significant fineness of the grinding. In 
fact the standard sieve for determining fineness now generally used on the 
continent of Europe has seventy meshes per lineal centimeter, which corre¬ 
sponds to 175 meshes per lineal inch, or over 30,000 meshes per square inch. 
Not more than about twenty-five per cent of the cement should be held on a 
-sieve of this degree of fineness.* The author of this work recommends that 
n sieve of 120 meshes per linear inch (14,400 per square inch) be used, and 
that the residue on this sieve shall not be more than twenty (20) per cent. 
This requirement can now be readily complied with by all the leading manu¬ 
facturers of Portland and slag cements, f 

The French Commission advocate, in testing for fineness— 

1. Separating it into four grades by using sieves as follows: 


Approximate 
Number of 
Sieve. 

Number of Open¬ 
ings per Linear 

Number of Open¬ 
ings per Square 

Size of Wire 

Size of Openings 

Inch. 

Centi¬ 

meter. 

Inch. 

Centi¬ 

meter. 

In Inches. 

In Milli¬ 
meters. 

In Inches. 

In Milli¬ 
meters. 

50 

50 

18 

2,500 

324 

.008 

0.20 

0.014 

0.36 

80 

80 

30 

6,400 

900 

.006 

0.15 

0.007 

0.18 

175 

175 

70 

32,400 

4,900 

.002 

0.05 

0.0035 

0.09 


2. This test to be made on a sample of 100 grams, with sieves about 
12 inches in diameter. 

3. Hand-sifting to be considered finished when not over 0.1 gram 
passes under the action of 25 movements. 

4. The employment of a shaking-machine is recommended, especially 
for the Ho. 175 sieve. 

5. The results should be given as the total percentages which failed to 
pass each-sieve, beginning with the finest. Thus the percentage held by 
the Ho. 175 sieve includes the percentages stopped on the other two, and 
the percentage given for the Ho. 80 sieve would include that held on the 
Ho. 50 sieve. 


* It has been customary in the United States to specify a sieve of 50 meshes per 
lineal inch, but occasionally a sieve of 100 meshes per inch has been used. The former 
size has no significance whatever in determining that degree of fineness requisite to 
proper action of the cement, and the latter is too coarse to have much or any value. 

f This is also the standard chosen by Mr. J. W. Sandeman, M. Inst. C. E., in Trans. 
Inst. C. E., vol. cxxi. (1894-5) p. 215, and it has also been adopted by some officers of 
•the U. S. Engr. Corps. 



























TESTING OF CEMENT. 


411 








X 


Apr*- — 

600 






» / 








s.# 


T / 

i 




400 

/ 

I / 

/ / 

6S 

/ 

C: /J 


IIP-" 


r 

- 1 _ 





/ 

/ 

/ 

/ 

A 


n 1) 

"igpf 


—X 

5> /J 

y ~ oL 


200 

$ 

/ 

/ j 

/ a 
/ / 

/ / 





6 / 










A 


V Wit 

r/rj 

0 


20 


Fig. 329. —Showing Effect of 
Sifting a Coarse Portland 
Cement through a No. 180 
mesh sieve (Trans. Inst. 
C.E., vol. 84.) 




Fig. 331. —Showing Effect of Regrinding Portland Cement on Mortar, 1 C. : 3 S. First 
grinding left only 6.5# on a No. 175 sieve (30,000 meshes per square inch). After 
second grinding it all passed this sieve. (Tetmajer, vol. vn.) 

















































































412 


THE MATERIALS OF CONSTRUCTION. 


Dr. W. Michaelis, the great German specialist, recommends* that two 
sieves be used, No. 75, and No. 150 (30 and 60 meshes per cm.), and in 
addition to these the Schone washing apparatus with rates of upward flow of 
the alcohol of 2.8 inches per minute, giving particles of cement which would 
pass a No. 300 sieve (120 per centimeter), and also of 1 inch per minute 
upward velocity, giving particles which would correspond to those passing a 
No. 600 sieve (240 meshes per centimeter). This washing process, added to 
the use of the two sieves, would enable one to graduate the cement as 
follows: 


Number of Meshes per 

Diameter of Wire 

Width ot Mesh 

Area of Mesh 

Square 

Square 

In Milli- 


In Milli- 


In Square 

In Square 

Centimeter. 

Inch. 

meters. 


meters. 


Millimeters. 

Inches. 

900 

4,200 

0.133 

0.0052 

0 20 

0.0080 

0 04 

0.0000610 

3,600 

23,500 

0.067 

0.0026 

0.10 

0.0040 

0.01 

0.0000150 

15,000 

97,000 

0.033 

0 0013 

0.05 

0.0020 

0.0025 

0.0000040 

60,000 

390,000 

0.002 

0.00008 

0.02 

0.0008 

0.0004 

0.0000006 


The relation between the largest diameter of particle and the rate of 
upward flow for absolute alcohol and Portland cement he finds to be 


d = 0.036/ 1 , 


where d — largest diameter in millimeters, and v — upward velocity of flow 
in millimeters per second in the cylindrical part of the washing apparatus. 

As a result of this further analysis for fineness it appears that the conclu¬ 
sions drawn from an analysis with the No. 7 5 and the No. 175 sieve (30 and 
70 per centimeter) may be entirely erroneous. Thus among the many 
analyses given by Michaelis in these articles are the following two analyses 
of cement ground in the same manner, on French bulirstones, 5 ft. in 
diameter: 


Sieve-gauges (Meshes per Linear Inch), where Diameter of 
Wire = Width of Mesh. 

Sample No 1. 

Sample No. 2. 

Parts. 

Total 

Passing. 

Parts. 

Total 

Passing. 

Retained on No. 75 sieve.. 

0.65# 

99.35# 

1.55# 

98.45# 

Passed No. 75 and retained on No. 175 sieve. 

7.75 

91.60 

7.40 

91.05 

“ “ 175 “ “ “ “ 300 “ . 

42.98 

48 62 

19.71 

71.31 

“ “ 300 “ “ “ “ 600 “ _ 

“ “ 600 sieve... 

17.75 
30 87 

30.87 

25.27 

46.04 

46.04 


100.00 


100.00 



* Thonindustvie-Zeitung {Clay-industry Gazette ), Berlin, Aug. 24 and Nov. 23, 1895. 
Dr. Michaelis first introduced the No. 175 sieve in Germany about 1875. 




















































TESTING OF CEMENT. 


412a 


The total percentage passing the No. 175 sieve was 91.G0 for sample 
No. 1, and 91.05 for sample No. 2. This would appear to give No. 1 a slight 
advantage. There was stopped at the next stage, however, 43 per cent of 
No. 1 and only 20 per cent of No. 2, thus leaving only 48.62 per cent of 
No, 1 to pass the 300 sieve, while of No. 2 there passed 71.31 ]:>er cent. 
Finally, there was but 31 per cent of No. 1 to pass the washing test, which 
corresponded to a No. 600 sieve, while 46 per cent of No. 2 passed this last 
test of fineness. It thus appears that sample No. 2 is much finer ground 
than No. 1, although this would not appear from the most severe sieve-test 
it is possible to make. 

The essential part of the Schone apparatus is shown in Fig. 331m It 
consists of a bent glass tube, conical from I) to C, but cylin¬ 
drical from C to B. The tube AHKL is also a glass tube, 
having an escape opening at N. The material to be assorted 
is placed in the conical portion CD, and the washing liquid is 
introduced at G and escapes at K, through an orifice about 
y 1 ^ in. in diameter, under any fixed head NT, controlled by 
the rate of admission at G. This head NT is the argument 
which is read on the graduated tube when in use to give the 
rate of flow, and hence the rate of upward velocity in the 
cylindrical portion CB. When properly standardized, the up¬ 
ward movement in this portion can be read from a diagram, or 
table, in terms of the head NT, which can be made a meter or 
more. The apparatus is defective as a quantitative separator, 
since there is no means of stirring the material in the conical 
part of the tube, and hence some of those particles which 
could readily be carried over for any particular upward 
velocity in CB will remain entangled in the mass of material 
left in the conical part DC. 

By using coal-oil on Portland cement the average di¬ 
ameters of the particles carried over for different velocities 
in CB very nearly agree with the formula given on p. 412 
for absolute alcohol and the largest diameters. Since these 
particles are quite angular, the word diameter is here used 
as the mean transverse dimension as measured on a micro¬ 
scope-scale. 

In some work carried out in the preparation of a thesis * 
under the direction of the author two samples of Portland 
cement, one American and the other German, both of stand¬ 
ard manufacture, were graded into five sizes by this method after having 
passed a No. 150 sieve. The sizes and the corresponding velocities of up¬ 
ward flow for each grade are given in the table next page, and the percent- 



Fig. 331<z. 
The Sclione 
Washing Ap¬ 
paratus. 


* By Edward Conzelman and F. A. Rapp. 
















4126 


THE MATERIALS OF CONSTRUCTION. 


GRADUATION OF PORTLAND CEMENT BY THE SCHONE APPARATUS. 


Percentages of Original Samples. 


Brand of 
Cement 

Carried by 
a Velocity 
of 0.38 mm. 
per Second. 
Maximum 
Diameter 
less than 
0.02 mm. 

Carried by 
a Velocity 
of 1.00 mm. 
per Second. 
Mean 
Diameter 
of 

0.030 mm. 

Carried by 
a Velocity 
of 1.78 mm. 
per Second. 

Mean 

Diameter 

of 

0.048 mm. 

Carried bj r 
a Velocity 
of 2.78 mm. 
per Second. 
Mean 
Diameter 
of 

0.068 mm. 

Carried by 
a Velocity 
of 4 00 mm. 
per Second. 

Mean 

Diameter 

of 

0.097 mm. 

Passed No. 

150 Sieve 
and resisted 
a Velocity 
of 4 mm. 
per Second. 
MeanDiam- 
eter of 
0.116 mm. 

Held on a 
No. 150 
Sieve. 
Mean 
Diameter 
of 

0.180 mm. 

Atlas (Amer.). 
Star (Stettin, 

45 

6 

9 

8 

7 

9 

16 

Germany)... 

36 

7 

9 

8 

8 

9 

23 





Diameter = 0.10 mm. 


Diameter = 0.03 mm. 


Diameter = 0.12 mm. 


Diameter = 0.05 mm. 


Fig. 3316.—Photo-micrographs of graduated Sizes of Portland Cement Grains, separated 
by the Author by Means of the Schone Washing Apparatus. 


Diameter = 0.18 mm. 
(100-150 Sieves.) 


Diameter = 0.07 mm. 





















TESTING OF CEMENT. 


413 


-40 


-36 


C.C 


c.c 


ages the weights of each grade were of the entire sample. This table shows 
that only about 40 per cent of the cement was of the finest grade, and prob¬ 
ably not more than half of this was of the impalpable powder which really 
composes the active portion of the cement. 

None of the other grades showed any tendency to harden after 
washing thoroughly with gasoline, drying, and wetting with water, 
whereas the finest grade showed its normal 
hardening properties when so treated. 

These specimens, shown in Fig. 3316, have 
the appearance of coarse sand-grains under the 
microscope, and they are certainly quite inert 
and serve as so much sand in the hardening of 
cement-mortar. These analyses show the very 
great improvement which may yet be made in 
Portland cement by finer grinding. 

311. The Thoroughness of the Burning is 
indicated by the specific gravity of the ground 
cement. If the cement is underburned, it is rel¬ 
atively light. This test is, therefore, really a 
test for specific gravity. 

Since the volume of a given weight of cement 
depends altogether on the way in which it is 
shaken down or compacted, it is impracticable to 
determine specific gravity by weighing measured 
volumes. The specific gravity of cement is found, 
therefore, by means of an apparatus like that 
shown in Fig. 332. This vessel is filled with 
benzine or turpentine,* up to the zero gradua¬ 
tion on the inserted tube or above. A definite 
weight of cement is slowly dropped into the top 
of this tube, care being taken to allow all air- 
bubbles to escape, when the rise of the liquid in 
the tube will indicate the true volume of the 
cement which has been added. If metric units 


-38 


-31 


C.C 


C.C 


-30 


cc 



have been used, then the specific gravity of the Fig 332 .-Apparatus for De¬ 
cement is equal to the weight of the quantity termining the Specific Grav- 
added in grams divided by the increase of volume ity of Cement, as used by 
in cubic centimeters. Since well-burned Port- the Author. One-third 
land cement has a spceific gravity of more than natural size. 


* While the cement has no tendency to set or harden when turpentine is used, yet 
the volume of this liquid is so sensitive to changes in temperature that it is not advisable 
to use it unless the cement, the turpentine, and the vessel all have the temperature of the. 
room, and this latter remains constant during the test. 






















414 


THE MATERIALS OF CONSTRUCTION. 


3.05 , this figure may be taken as a minimum specific gravity to be used 
in a specification. 

In making this test it is necessary to see that all lumps are thoroughly 



Fig. 333. —Graphical liepreseutation of the liate of Setting of Portland Cement at 
Various Temperatures, automatically recorded by the Apparatus shown in Fig. 334. 
(Tetmajer.) 

pulverized and dried. To insure this it should be passed through about a 
No. 80 sieve, that remaining on the sieve to be added to the specimen. This 



Fig. 333a.—Increase in Temperature at the Centre of a Heavy Mass of Portland-cement 
Concrete 11.5 ft. thick, as a result of Chemical Action. (Rep. Fr. Com., vol. iv, 
PI. III.) 

test should be accurate within one per cent, or to within three in the second 
decimal place. 




















































































































TESTING OF CEMENT. 


415 


This test is not usually applied to natural cements, since it is not supposed 
that they will be burned either so carefully or at so high a temperature as 
is required for Portland cement. 

312. The Rate of Setting. —In the process of hardening of cement-mortar 
theie aie two well-defined stages, known respectively as the beginning and 
the ending of the setting. A quick-setting cement may begin to set within 
a very few minutes after wetting, while a slow-setting cement may require 



Fig. 834. —The Ainsler-Latfou Apparatus for Automatically Registering the Rate of 

Setting of Cements as given in Fig. 333. 

more than twenty-four hours before it begins to set. Usually the setting 
progresses rapidly after it has begun, as indicated in the curves in Fig. 333. 
These curves have been automatically recorded * by the apparatus shown in 
Fig. 334. This setting action is always accompanied by a slight rise in 
temperature. In fact, with quick-setting cements the temperature curve 
is a truer index of the setting period than the mechanical tests of firmness 
which are usually employed for this purpose. As long as the temperature 


* Taken from Prof. Tetmajer’s Reports, vol. vi 



































































































































































































































416 


THE MATERIALS OF CONSTRUCTION. 


continues to rise the setting action is in progress, and the rate of setting is. 
well indicated by the rate of increase of temperature. 

An excellent illustration of the evolution of heat by chemical action in 
the hardening of cement is furnished by Fig. 333«. Here the rise in tern* 
perature was observed for sixteen days at the centre of a mass of Portland- 
cement concrete 11.5 feet thick. The temperature rose 47.5° C. (85.5° F.) 
in four days, and reached its maximum increase of 52° C. in seven days, after 
which it fell otf very slowly. Both the temperature-curve and the harden¬ 
ing-curve are automatically recorded by the apparatus shown in Fig. 334. 
This apparatus was manufactured by Messrs. J. Amsler-Laffon & Son, 

Schaffhausen, Switzerland. Its operation is too 
complex to be explained here. It is in satis¬ 
factory use, however, in Prof. Tetmajer’s labora¬ 
tory at Zurich. With slow-setting cements the 
rise of temperature cannot be observed with 
accuracy, and is smaller in amount than in the 
case of quick-setting cements. In such cases, 
the heat developed is dissipated because of its. 
slow generation, and does, therefore, not be¬ 
come sensible to thermometric measurement. 

The usual method of determining the set¬ 
ting period is by means of such an apparatus. 
as shown in Fig. 335. By this means a needle: 
of a particular diameter and loaded with a. 

--—-specified weight is allowed to rest upon the 

Fig. 335. — the Yicat-needle ca p e 0 f mortar, which for this test should be 

Apparatus. mixed neat, and the setting is determined by 

the depth of penetration of the needle. When the needle ceases to reach 
the bottom of the cake, setting is supposed to have begun; and when it 
rests wholly on the top, the setting is supposed to have been completed. 
The temperature-curve, however, indicates a continuation of this action for 
some time after the needle ceases to penetrate the mass. The method 
commonly employed in America is that recommended by the American 
Society of Civil Engineers, which is as follows: 

A neat cement-mortar having a stiff, plastic consistency is placed in a form two 
or three inches in diameter and one-half inch thick. When a needle one-twelfth 
inch in diameter, weighted with one-fourth pound, ceases to penetrate the entire 
mass, setting is said to have begun ; when a needle one twenty-fourth inch in diam¬ 
eter, carrying one pound, will not penetrate the mass at all, setting is said to have 
been completed.* 

In this test, those cements which set completely in one-half hour or less 
are known as quick-setting. Those requiring much more time, slow-setting. 
It must not be supposed that these terms are used rigidly with this limit. 

* The French Commission recommend a needle 1.13 mm. diameter and loaded 
with 300 grams for both of these tests. This needle is 0.045 inch diameter and just 
1 square millimeter in area. The load is 11 ounces. 


























TESTING OF CEMENT. 


417 


In Germany and France a needle one millimeter in diameter is loaded 
with a weight of 300 grams, and the beginning and the end of the setting 
period is indicated by the time when this needle ceases to penetrate the 
entire mass, and when it ceases to penetrate it at all, respectively. 

The time when the setting has been completed can be approximately 
determined by efforts to indent the surface with the finger-nail. When the 
surface offers some appreciable resistance to such indentation, the cement 
may be said to have set. From results of tests given in Chapter XXX it 
does not seem to he as injurious to the final strength of the mortar to use it 
after it has begun to set as it has commonly been supposed. 

313. The Test for Soundness. —This is a test of the permanency of vol¬ 
ume of a cement-mortar, or of its resistance to disintegrating influences. 
Although wrong mixtures, improper calcining, and coarse grinding may 
lower the strength of a cement, a strong tendency to swell or to disintegrate 
is absolutely fatal, not only to the mortar, but also to the structure in which 
it is used. In America reliance in this matter has been placed on the good 
record of the particular brand, rather than on actual tests to determine the 
“soundness.” Professor Tetmajer of Zurich, the leading authority now 
on cement-testing, having tried various methods of determining this prop¬ 
erty, recommends for Portland cement the boiling test described below. 
For slag-cement and for the natural cements he has not found any satisfac¬ 
tory means of determining this quality by a short test. 

While “ soundness” may be tested by a long maintenance of the cement- 
cakes under water and in the air for many years at least, this is of course 
not possible in practice. 

It is true that all cements swell under water and shrink in the air, but 
these changes are usually inappreciable. A dangerous swelling of volume 
under water may be caused by an excess of quicklime (CaO) in an over¬ 
burnt condition, which resists the slacking action of water for a consider¬ 
able time. These cements maybe called “lime-expanders.” 

The sulphur compounds of lime (CaS and CaS0 4 , or gypsum) may cause 
the cement to disintegrate in air by oxidation and the absorption of water 
(becoming CaS0 4 -(- 2H 2 0 and CaS0 4 -f- 7H 2 0). 

If magnesian limestone, or dolomite, forms a considerable portion of the 
raw ingredients, after years of apparent soundness, the cement may disin¬ 
tegrate from swelling, if under water, due to the final slacking of the mag¬ 
nesia. Professor Tetmajer states, however, that he has never met with any 
actual Portland cement which has failed in a test from the presence of the 
sulphur or the magnesia compounds. It seems, therefore, that the only 
•source of unsoundness to he anticipated is an excess of quicklime, and this 
is best determined by the boiling test. 

314. The Boiling Test. —This test has been practised for the past twenty- 
iive years, and has received almost universal sanction. At the Fifth Inter¬ 
national Convention for Unifying Methods for Testing Construction 


418 


THE MATERIALS OF CONSTRUCTION. 


Materials, held in Zurich, Sept. 1895, the following rules for conducting 
this test were recommended by a committee of the leading experts of 
Europe, Dr. Michaeiis being chairman, who originally proposed this test 
about 1870. 

I. The rapid test of hydraulic cements for constancy of volume consists in the 
application of warm baths at temperatures of from 50° to 100° C. (122° to 212° F.). 

II. Manner of Making the Test-pieces. —Enough water is used to bring the neat 
cement, after proper working, into a plastic state. Two balls from 40 to 50 milli¬ 
meters (1.5 to 2 inches) in diameter are formed by hand and kept in moist air, resting 
on some nonabsorbent material. (Sand mixtures are not to be subjected to this test, 
neither are briquettes which are to be tested for strength to be so treated.) 

The employment of tension briquettes and cylindrical disks from 50 to 100 milli¬ 
meters (2 to 4 inches) in diameter and from 15 to 30 millimeters (f to 1£ inches) in 
thickness is likewise permitted. 

III. Duration of Previous Hardening. —Until set has taken place test-pieces must 
be kept in moist air. Portland, slag, Pozzuolana, and Roman cements will be 
uniformly kept thus for twenty-four hours; very slow-setting ones for forty-eight 
hours. Hydraulic limes and all cements that have not completely set after forty- 
eight hours will be allowed seventy-two hours for previous hardening. 

IV. Treatment in the Warm Bath. —The previously hardened test-samples are 
placed in a water-bath at ordinary temperature, which is then gradually—not in 
less than thirty minutes—heated to the prescribed temperature and kept there.. 
After three hours at the prescribed temperature the test is interrupted, the test- 
pieces are taken out of the bath, and after having cooled sufficiently, examined as 
to their condition. They must not be chilled suddenly by means of cold water. 

For each warm-bath test the water must be renewed. The temperature of the bath 
Will be: 

For Roman cements and hydraulic limes, 50° C. (122° F.); for Portland, slag, and 
Pozzuolana cements, 100° C. (212° F.). 

V. In order to be considered of absolutely constant volume the test-sample must, 
during this test, remain perfectly sound and entirely free from cracks and warping. 



Fig. 336. —Showing Methods of Failure of Cements under the Boiling Test.* 

If the ball cracks slightly in this test or disintegrates somewhat as shown 
in Fig. 336, it should be considered at least doubtful, although it might 
not fail in actual practice. 

A modification of this test is to maintain a bath at a little less than the 
boiling temperature, in order to prevent the wearing action of the boiling 
water. As it is difficult, however, to maintain such a temperature, the boil- 


* These cuts are taken from Professor Tetmajer’s Communications for 1893. 







TESTING OF CEMENT. 


419 


ing test is to be preferred, using the least fire which will maintain this tem¬ 
perature. At the end of this three-hour period the specimens will be found 
to be extremely hard and solid, like stone. No other test for soundness need 
be employed. This test is to be employed only with Portland cements, as 
probably few natural cements would stand it. No satisfactory test for the 
soundness of natural cements has been found, and the fact that these cements, 
which may go all to pieces in the boiling test, still stand well in service forms 
a strong argument against the drawing of adverse conclusions from this test 
when applied to Portland cements. The question of what tests to apply to 
determine the weathering qualities of cements is as yet unsolved. 


TESTING THE STRENGTH OF CEMENT. 


315. Tensile Test Sufficient. —Although cement-mortar and concrete are 
commonly subjected to a compressive stress only, and hence the strength in 
compression is of the greatest importance, the only test of strength usually 



Fig. 337.— Showing the Ratio of the Tensile to the Compressive Strength of Portland- 
cement Mortar, 1 C.: 3 S., by Weight. Each point plotted is the average of 550 tests of 
each kind. Equation of curve, R= 8.64 -f 1.8 log A. (Data taken from Tetmajer's 
Communications, vol. vi.) 

made is that in tension. In Art. 20 it was shown that the strength of such 
materials in compression is really their strength in shearing, and for a gran¬ 
ular material the strength in shearing woull be expected to vary with the 
strength in tension. It was to be presumed, therefore, that the tensile 
strength of cement would have a definite relation to its compressive strength. 
The author is now able to establish this relation as shown in Fig. 337. 
Here 55 samples of Porthmd-cement mortar, one of cement to three of 
sand, by weight, were tested by Professor Tetmajer both in tension and in 









































420 


THE MATERIALS OF CONSTRUCTION . 


compression, there being fifty tests of each kind from each sample. One 
third of these were left to harden in air, and two thirds hardened under 
ivater. These fifty tension- and fifty compression-test specimens of each 
mixture were divided into five lots of ten each, and these were tested in five 
periods of time, namely, in 7 days, 28 days, 84 days, 210 days, and 1 year. 
The average ratios of the compressive to the tensile strength of the 550 tests 
of each kind made at each of the above periods are plotted in Fig. 337, and 
joined by the full line. The probable error of each of these ratios was also 
determined from the residuals obtained by comparing each of the fifty-five 
results with its average, and these probable error-limits are also indicated in 
the diagram. These limits are so uniform and so small as to lead to the 
necessary conclusion that the ratio between the compressive and the tensile 
strength of cement is a very rigid one for any given age, but that it increases 
with the age of the mortar. This curve is very nearly represented by the 
following equation, the maximum deviation of which from the observed locus 


is less than one half of one per cent 

Compr. strength 


Ratio 


Tensile strength 


= 8.64 + 1.8 log A f 


where A — age of the cement-mortar in months. The compression tests were 
made upon cubical forms. The value of this study is not so much the 
determination of the true relation between the tensile and the compressive 
strength of cement-mortar as it is to show that the tensile test is sufficient 
to determine compressive strength.* 

316. Standard Consistency of Neat-cement Test-specimens.—It has been 
found impracticable to specify any particular percentage of water for all 
kinds of cement, or even for all brands of one class, as of Portland 
cement, or of natural cement, or of slag-cement. A certain consistency of 
the gauged cement demands various percentages of water with different 
brands of the same class of cements. It is necessary, therefore, to have a 
standard method of fixing this consistency. The effect of using varying 
quantities of water with a single brand of cement is shown in Figs. 338 to 
343. When an excess of water is used the briquettes are greatly weakened 
for short periods, but the effect partly disappears with time. When too 
small a quantity of water is used, it requires too much work to thoroughly 
compact the briquettes, and the results are apt to be irregular. 

The French Commission have adopted a modified form of Prof. Tet- 
majer’s method of determining consistency, which is as follows: 

(1) Take one kilogram (2 lbs. 5 oz.) of cement, place it on a marble slab, 
arrange it in a crater-like form, and add at one pouring all the water which is to be 


* M. Feret has shown in An. d. Ponts et Chaussees, 7th series, vol. iv. p. 1, Fig 19 
(1896), that this ratio becomes greater for higher proportions of sand. In fact the com¬ 
pressive strength varies uniformly with the proportion of cement used, while the tensile 
strength is nearly constant for small proportions of sand but falls rapidly for the poorer 
mixtures. 




TESTING OF CEMENT. 


421 



Fig. 338.—Effect of Varying Percentages of Water used in Gauging Portland-cement 
Mortar, 1 C. : 3 S. Average results on five brands of cement. Each point plotted 
is the mean of fifty tests. (Tetmajer, vol. vn, 1894, p. 10.) 



Fig, 339 .—Effect of Varying Percentages of Water in Gauging Neat Portland Cement. 

{Jour. West. Soc. Engvs., vol. i. p. 82, Table XVIII.) 















































422 


THE MATERIALS OF CONSTRUCTION. 




ages of Water. (Wheeler, Rep. Chf. Engrs., U. S. A., 1894, p. 2332.) 




































































TESTING OF CEMENT. 


423; 



Fig. 341.—Effect of Varying Percentages of Water on Time of Setting of Neat Cement* 

(Wheeler, Rep. Chf. Engrs ., 1895, p. 2935.) 



Fig. 342.—Effect on the Strength of Louisville (Natural) Cement, Neat, of a Varying 
Percent of Water in Gauging. {Jour. West. Soc. Engrs., vol. i. p. 82, Table XVI.) 

used, this volume being that necessary to satisfy the conditions described in (2). 
The water to be either fresh or salt, as may be specified. The whole is then stirred 
and turned rapidly with a trowel for five minutes , counting from the instant the 
water was added. 

(2) With a portion of this gauged cement fill a vessel having an interior form of 
a truncated cone, 8 cm. (3J inches) in diameter at bottom, 9 cm. (3f inches) in 
diameter at top, and 4 cm. (If inches) deep, smoothing it off quickly on top with 
the trowel. 

Upon the centre of this top surface bring to bear normally and slowly a cylinder 
of polished metal 1 cm. (£ inch) diameter and weighing 0.3 kilogram (11 oz.), having 
a full, flat, transverse sectional base. The apparatus to be constructed so as to 






































































424 


TEE MATERIALS OF CONSTRUCTION. 


indicate the thickness of the film of mortar remaining below the cylinder when it 
ceases to settle under its own weight. Two tests to be made on the same cake. 

The consistency to be considered as normal when the cylinder stops just 4 inch 
from the bottom of the cake. 

For quick-setting cements use one half the amount of dry cement, and mix one 
minute instead of five. 



Fig. 343.— Effect of Varying Percentages of Water in Gauging Utica (Natural) Cement- 
mortar, 1 C. : 1 S. {Jour. West. Soc. Engrs., vol. i. p. 82, Table XV.) 

317. Normal or Standard Sand. —That the quality of the sand exerts a 
marked influence on the strength of cement-mortar is shown by Figs. 344 
and 345. These tests show the great superiority of calcareous over siliceous 


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Fig. 344.—Effect of the Quality of the Sand on Strength of Cement-mortar, 1 C.: 3 S. 
(Wheeler, Rep. Chf. Engrs., U. S. A., 1894, vol. iv. p. 2321.) 


sands in giving strength to the mortar. Evidently, however, sands con¬ 
taining small shells containing air-spaces should be excluded. 

To find the composition of a sand immerse it in cold hydrochloric acid, 
which will dissolve the calcareous portion. The residuum may then be 
separated into the insoluble siliceous sand and the clay, by rubbing and wash- 


























































TESTING OF CEMENT. 425 

ing, and thus its three significant constituents determined with sufficient 
accuracy for commercial purposes. 

Not only the strength but the permeability of mortar depends on the 
size of the sand-grains; and as the resistance to the decomposing action of 



Fig. 345.—Comparative Value of Different Sands in Portland-cement Mortar 18 
months old (in water). (Wheeler, Rep. Chf. Engrs., 1895, vol. iv. p. 2953.) 

frost and sea-water depends almost wholly on its impermeability, the life 
of the mortar, in exposed situations, is largely dependent on the character 
of the sand used. 

In order that tests of the strength may be comparable, therefore, it is 
necessary to choose a normal, or standard, sand. In Germany and in France 
natural sands are chosen, while in the United States a committee of the 
American Society of Civil Engineers recommended in 1885 the use of 
crushed quartz, such as is used in making sand-paper, of a size which passes 
a No. 20 sie v e and is stopped on a No. 30 sieve. This leaves all the grains 
with maximum dimensions of from 1 mm. to 1.5 mm. When the grains are 
so nearly of the same size and very angular or “ splintery ” the proportion 
of voids is very great, so that a mixture of 1 cement to 3 sand by weight will 
not be solid without a great amount of pounding on the briquette, which 
must be mixed dry to enable it to receive such treatment. 













426 


TEE MATERIALS OF CONSTRUCTION. 



Tig. 346.— Comparative Value of Three Kinds of Saud for Portland-cement Mortar, 

1 0.: 3 S. (St. Louis Water Dept., 1895.) 



Fig. 347,—Effect af Fineness of Sand on Strength of Portland-cement Mortar, 1 : 1 and 
1: 2. Age 6 months. (Wheeler, Rep. C/if. Engrs., 1895, p. 2972.) 


































TESTING OF CEMENT. 


427 


The French Commission have adopted the following: 

Normal or standard sand consists of sand found on the beach at Leucate, and is 
of three sizes: 

No. 1, passing a sieve of 1 mm. and retained on one of 0.5 mm. mesh. 

No. 2, passing a sieve of 1.5 mm. and retained on one of 1 mm. mesh. 

No. 3, passing a sieve of 2 mm. and retained on one of 1.5 mm. mesh. 

Simple normal sand is construed as meaning No. 2. Composite or 
mixed normal sand is construed as meaning all three sizes in equal parts, 
this mixture approaching closely the sand ordinarily employed in engineer¬ 
ing works. The finest grade, No. 1, corresponds to such fine sand as is 
found in the sand-dunes along our sea and lake shores, while the coarsest, 
No. 3, corresponds to the very coarse sand taken from the bed of a rapidly- 
flowing river. The composite or mixed sand is exclusively used in standard 
tests of mortar. This is to be commended, as it gives fewer voids, and a 
mixture of 1 cement to 3 sand readily makes a perfectly solid test specimen. 
The above sieves, having meshes of 0.5, 1.0, 1.5, and 2 millimeters, would be 
found to have approximately 35, 20,15, and 11 meshes per inch respectively. 



Fig. 348.—Showing Effect of Varying Fineness of Clean River-sand in Cement-mortar, 

1 C. : 3 S. (Wheeler, Rep. Chf. Engrs., vol. iv, 1894.) 


In place, therefore, of using a 20-30 sand in making up standard mortar- 
test specimens, as has become customary in America, in accordance with 
the American Society of Civil Engineers Committee’s recommendation, the 
French are using a sand composed equally of three grades, which are respec¬ 
tively 11-15, 15-20, and 20-35 sieve samples. This gives sand-grains vary¬ 
ing from 0.5 mm. to 2.0 mm. in size, or a variation in size of 300$ of the 
smallest, while the American Society of Civil Engineers’ standard allows 




























428 


THE MATERIALS OF CONSTRUCTION. 



Fig. 349.—Effect of Size of Limestone Screenings when used as Sand in Portland- 
cement Mortar, 1 C. : 3 S. (Wheeler, Rep. C/if. Engrs., 1894, vol. iy.) 


o 



Fig. 350,—Variation in Volume of Different Grades of Sand by the addition of small 
quantities of water. (Wheeler, Rep. Chf. Engrs., 1895, p. 2935.) 


l/r/?£ 0F 6AA/P AS PIOTTEO 


























































TESTING OF CEMENT. 


429 


but 50$ variation in the size of the sand-grains for the standard mortar- 
tests. 

318. Standard Consistency of Cement-mortars.—The standard cement- 
mortar is composed of one part of cement to three parts of standard sand, 
by weight. The great variation in volume of sand with varying percentages 
of water, as shown by Fig. 350, precludes the volume measurement even of 
the sand, while with the cement there is no fixed relation between volume 
and weight. It has been customary for many years in Germany to use the 
minimum amount of water which would enable this mixture to be com¬ 
pacted in a briquette by the action of what is known as Bbhme's hammer 
(see Fig. 352), in the use of which 150 blows is given to each briquette. As 
this is a condition very far removed from those of actual practice, it has 
always been objected to in other countries, and has never come to be stand¬ 
ard in America. When a greater quantity of water is used, however, so as 
to give a plastic mortar, it cannot be compacted by pounding and it becomes 
more difficult to obtain uniform results. The French Commission have 
studied this question most effectually, and, while they are forced to still 
recognize the dry mixture as above described, they strongly recommend 
the use of plastic mortars, and express the hope that the German standard 
method of preparing these specimens will fall into disuse. Their recom¬ 
mendations on this subject are as follows: 

1. Standard plastic cement-mortar shall be composed of one part of cement (250 
grams) to three parts of mixed normal sand (750 grams), this being composed of 
equal parts of numbers 1, 2, and 3, as described in Art. 317. These will be mixed 
thoroughly before water is added, on a marble slab, and then gauged with the full 
quantity of water, either fresh or salt as the case may be, and vigorously stirred and 
worked for five minutes. 

The quantity of water to be used to be such that when the vessel described in 
Art. 316 is filled with the mortar and smoothed off, a few strokes of the trowel upon 
the sides of this vessel will cause the mortar to liquefy slightly at the surface. 

For cements which set rapidly the total quantity of materials used to be reduced 
to 500 grams, and the gauging to be continued for one minute instead of five. 

2. Standard dry-cement mortars shall be composed of one part of cement (250 
grams) to three parts (750 grams) of standard sand No. 2 (described in Art. 316), 
these to be mixed while dry on a marble slab, and then an amount of water added 
equal to one sixth of that necessary to use in bringing one kilogram of the same 
kind of neat cement to the standard consistency described in Art. 316 plus 45 grams 
additional.* 

3. If other proportions are desired than one of cement to three of sand, it is 
recommended that one of cement to two of mixed standard sand, and one of cement 
to five of mixed standard sand, be used ; these also to be regarded as standard, rich, 
and poor mortar, respectively. The amount of water to be used m each case to be 
such as to produce a plastic mortar which will satisfy the conditions named above in 1. 


* For the standard dry mortars of varying proportions of sand, and for all kinds of 
cement, the amount of water to use was found to be, in grams for 1 kg. of the dry 
mixture, w = f H / (7 + 45, where \V = weight of water in grams required to bring 1 kg* 
of the pure cement to the normal consistency described in Art. 316, and C = weight in. 
kilograms of the cement entering into the dry mixture. 




430 


THE MATERIALS OF CONSTRUCTION. 


In place of the hand-mixing on a slab, as described above, the author has 

nsed with very satisfactory results the Faija 
mechanical mixer, made by Riehle and shown 
in Fig. 351. Something of this sort is espe¬ 
cially helpful in the case of sand mixtures, the 
sand and cement being first mixed dry and 
then from three to five minutes after wetting. 

The St. Louis Water Department use for 
neat cement a “jig,” consisting of a pair of 
cups mounted vertically on a reciprocally mov¬ 
ing head-piece, operated by a very rapid circular 
motion, like the familiar “ milk-shake ” appa¬ 
ratus. (See drawings and description in Engr. 

News , vol. xxv. p. 3, 1891.) 

319. The Formation of the Briquettes.—The following rules for forming 

the briquette are based largely on the Report of the French Commission, 
but they also fairly represent the best current American practice. 

A. For Standard Plastic Mortar, 1 Cement to 3 Sand. 

(1) The briquette to be of the form shown in Fig. 355 or Fig. 356, 
having just one square inch of minimum cross-section.* 

(2) The moulds to be quite clean, and to be rubbed with an oiled or 
greased linen cloth, and placed on a plain marble slab, or plate-glass, or 
polished metal surface. Six moulds to be simultaneously filled to overflowing 
(if the cement is slow-setting, and but four moulds to be filled if it is quick¬ 
setting), the entire amount required for one mould to be inserted at one 
time. The mortar to be pressed into the moulds with the fingers, and a few 
strokes given to the side of the mould with the trowel. This having been 
done for the entire set (of six or four as the case may be), the excess of 
mortar is carefully removed with a straight-edged blade resting on the top 
edge of the moulds, but without exerting any compression on the material 
below this plane. The surface is then polished off with the trowel, and the 
whole covered with wet cloths, and kept from sun and wind, in a saturated 
atmosphere, and at a temperature of from 60 to 70° F. When making 
plastic briquettes of neat cement, it may be best to allow them to stand a 
while before removing the excess of material and polishing off. 

(3) After the mortar has set (at the end of 24 hours, or sooner) the 
mould is tapped lightly on the side to loosen the briquette from the bed¬ 
plate, when the mould is unlocked and removed from around the briquette. 
These are not raised from the plate (if the moulds are removed inside of 24 
hours), but are covered with wet cloths until 24 hours have elapsed from the 
time of mixing with water. 

* The European standard section is 5 sq. cm. or 0.8 sq. in The ordinary American 
form of briquette (Fig. 354) should be abandoned at once, since it is impossible to pre¬ 
vent such briquettes of neat Portland cement from breaking in the clips. 



Fig. 351. 

















































TESTING OF CEMENT. 


431 


For very quick-setting cements the time period in air for neat cement 
may be reduced to one hour, and for mortar briquettes to three hours. 

A careful weighing of the briquettes when removed from the moulds gives 
a very good check on the uniformity of their composition. 

(4) At the expiration of the period described in (3) the briquettes are 
placed in their required medium till tested. If they are placed in fresh 
water, this should be changed as often as once a week. If placed in sea-water, 
it should be changed every two days for the first week, and then once a 
week. The water-volume should he at least four times that of the briquettes 
immersed in it. 

If the briquettes are to harden in air, this should be kept near the point 
of saturation, and they should be protected from all air-currents and from 
the rays of the sun. The temperature of the medium, whether of air or 
water, should remain from 60° to 65° F. (15° to 18° C.). 

(5) The tensile testing-machine to be so arranged as to give a uniform 
imposition of the load at the rate of 12 pounds (5 kg.) per second. The 
form of the grips to be that shown in Fig. 363. 

(6) Standard tests of cement-mortar to be made at the end of 7 days, 28 
days, 3 months, 6 months, 1 year, and 2 years, all computed from the time 
of gauging. For mortar made from quick-setting cement the shortest period 
to be 24 hours, and for quick-setting neat cement briquettes the short periods 
to be 3 hours, and 24 hours from the time of gauging. 

(7) So far as possible the six briquettes made from a given gauging to be 
divided uniformly among the lots to be tested at different periods. Thus if 
tests are to be made after six such periods, as named above, then one briquette 
from each gauging to be assigned to each period. 

A single result for any period to be the mean of the tests on six briquettes, 
defective samples to be rejected, however, and the mean to be derived from 
the remaining perfect tests, all the facts to be indicated on the record. 

The results to be given as so many pounds per square inch (kilograms 
per square centimeter) tensile strength on the standard form of briquette of 
one square inch (5 sq. cm. in Europe) in cross-section. 

B. For Standard Dry Mortar , 1 Cement to 3 Sand. 

(1) All the conditions specified in A to be complied with. In addition 
to these the following rules will be observed : 

(2) At the moment of mixing, the cement, the sand, the water, and the 
air to be at a temperature between 60° and 65° F. (15° to 18° C.). After 
the moulds are filled to overflowing, and the mortar has been pressed to place 
with the fingers, it will be pounded on the surface with a heavy spatula, 14 
inches long over all, including the handle, and having a surface of blade of 
four square inches (25 sq. cm.) and weighing 9 ounces* (250 gr.). The 

* No cut of this is given. If the blade itself is to weigh 250 gr., it would be, say, 
one inch wide, one-half inch thick, and four inches long. 





432 


THE MATERIALS OF CONSTRUCTION. 


briquette to be beaten at first with light strokes near the ends, then towards 
the centre. These to be followed by heavier strokes, always following the 
same course over the surface of the briquette, and continuing this treatment 
till the mass becomes somewhat plastic and water begins to appear at the 
surface. The surface is then scraped and smoothed off as before. 

For many years standard cement-mortar briquettes have been formed in 
Germany almost exclusively by the use of a machine shown in Fig. 352, 



Fig. 352. —Dr. Bolirae’s Hummer for making Cement Briquettes. 


which is the invention of Prof. Bohme of Charlottenburg. The hammer is 
driven by a wheel with ten cams, connected by simple gearings with a crank 
and handle. The steel hammer weighs four and one-half pounds. This 
apparatus may be used for making either tension- or compression-test speci¬ 
mens, and is preferably used when these are made of standard mortar mixed 
dry. There is an automatic stop which acts at the end of 150 strokes, this 
being the usual number of blows given to each test-specimen. Fig. 353 
shows an apparatus used by Prof, von Tetmajer and which has now been 
recommended for general use to the Fifth International Convention for 
Unifying the Methods of Testing Engineering Materials, which met at 
Zurich in September 1895. The French Commission have not included 
either of these kinds of apparatus in their standard specifications given above. 

320. The Form of the Briquette.-—After nearly a half-century of experi¬ 
menting on a great many different forms of briquettes, two leading forms are 
now used to the practical exclusion of all others. The English form shown 
in Fig. 354, having a minimum section of one square inch, is used in England 
and in America, and the German form shown in Fig. 355, having a minimum 



































TESTING OF CEMENT. 


433 


section of five square centimeters, is used on the continent of Europe, having 
recently been recommended by the French Commission. 

A great objection to the English standard form shown in Eig. 354 is that 
a very large proportion of briquettes of neat cement over four weeks old 
(about 50 oer cent) break in the clips and not on the minimum cross-section. 



Fig. 353. —Tetmajer’s Apparatus for 
Compacting Dry-mortar Briquettes, 
with an adjustable height of drop. 
( Fr. Com. Rep., vol. i. p. 287, and 
also Zurich Laboratory Communica¬ 
tions, vol. vn. p. 118 ) 



Fig. 354.—Standard Form of Briquette used 
in England and America. Full size. 


This is partly the fault of the small bearing-surface provided in the form o. 
clips used, but it is also largely due to the form of the briquette. The angle 
which the two bearing-surfaces form with each other is small, and the com¬ 
pressive stress resulting is correspondingly large, so that the briquette is apt 
to fail in the plane of the bearings from a combined vertical tension and a 
lateral compressive stress. 

The conditions which should be fulfilled in the form of a cement 
briquette for tensile tests are: 

(1) The bearing-surfaces in the clips should form an angle with each 
other of more than 90°. 

(2) The minimum section should be removed far enough from the plane 
of the bearings in the clips to insure a nearly even distribution of stress over 
this minimum section. 

(3) The minimum section should be small enough to insure rupture on 
this portion of the briquette, but the reduction should be by gentle curves. 

The English form (Fig. 354) is very defective in the first requirement, as 






































434 


THE MATERIALS OF CONSTRUCTION . 


i *• 



Fig. 355. —The European Continental Form of Briquette. 



Fig. 356.—New Form of Cement Briquette designed by the Author. Area of Cross 

section is -£■ square inch. Full size. 











TESTING OF CEMENT. 


435 


this angle is only about 60°, while the German form in this respect is excel¬ 
lent, its angle being 100°. 

Both forms are defective in the second requirement, as they are shortened 
np from reasons of economy and convenience. 

The German form, Fig. 355, is defective as to the third requirement, in 
that the reduction of section is too sudden. 

The author has devised and used a modification of the German form, as 
shown in Fig. 356, and he finds that it gives over twenty-five per cent greater 
strength than the English form, and.the briquettes never break in the clips 
he uses with it, shown in Fig. 363. The greater strength of this form 
results from the more even distribution of stress across the section of rupture, 
owing to the farther removal of the bearing-surfaces of the clips, while the 
large angle formed by these surfaces is maintained. While this of necessity 
makes a much larger briquette, it would seem to be the only way to secure 
a form which will develop the real strength of the material. 

321. To Find the Distribution of Stress over the Minimum Section of a 
Cement Briquette. —The following is a development of the theory of the 
distribution of stress over the minimum section of a cement briquette, pub¬ 
lished by M. Durand-Claye in the Annales des Pouts et Chaussees in June 
1895.* Let M and JV, Fig. 357, be the points of application of the external 



forces applied to the briquette, which is here given a somewhat conven¬ 
tional form. As a result of the application of the vertical forces at M and 
W these points are raised to M' and N' with respect to the fixed axis AB , 
through the distortion of the specimen. The original lines NB, NC, and 

* Prof. Aug. Foppl (Bauschinger’s successor) has now shown that a greater tensile 
stress is actually developed on the outer fibres of stone beams than can be obtained on 
tension specimens, and he thinks this is because of the uneven distribution of stress over 
the cross-section of the tension-test specimen. (Communications from the Munich 
Laboratory , vol. xxiv, 1896.) 










430 


THE MATERIALS OF CONSTRUCTION. 


NA of the specimen now become N'B, N' C, and NA, and the stresses along 
these lines are proportional to the deformations N'B — NB, N'C — NC, 
and N'A — NA, respectively. Similar relations exist on the corresponding 
lines drawn from M. The total stress at the points A, C, and B, therefore, 
will be equal to the sum of the vertical components of the stress at each 
point arising from the external forces at the two points of application 
M and N. 

Let a, j3, and a' represent respectively the angles which the three lines 
from N f to B, C, and A form with the vertical. 

Now the stretch of the lines ND, NB, NC, and NA due to the displace¬ 
ment NN is as 1, cos ex, cos /3, and cos ex', respectively, and the propor¬ 
tional stretch of a line is the total stretch divided by the length of the line; 
hence the proportional stretch of these lines is as 1, cos 2 ex, cos 2 (3, and cos 2 
a', respectively. 

But the stress is as the proportional stretch; hence the stresses along the 
lines NB, NC, and NA are as the squares of the cosines of their respective 
angles with the vertical. Since we are only concerned with the vertical 
components of these stresses, and since these are respectively equal to the 
inclined stress into the cosine of the same angle, the vertical stresses at B, 
C and A due to the external force at N are to each other as cos 3 a, cos 3 (3, 
and cos 3 a'. 

The total vertical stress at each of these points, however, is the sum of 
the two stresses arising from the external forces at both M and N; hence 
it follows that if we represent by R the total vertical stress at A and B, and 
by r 0 the total vertical stress at C, we have 

R _ cos 3 (x 4- cos 3 a' 

r 0 ~ 2 cos 3 (3 .' ' 

By trial the law of the distribution of stress over the section AB, by 
-equation (1), is very nearly that of a parabola. Making this assumption, 
and knowing that the area of the exterior portion of the rectangle enclos¬ 
ing a parabolic segment is one third that of the rectangle, we have, for the 
mean stress over this section, 


1 4- 2 0 

P 1 ' ^ n 

r=-=r a +- { R-r a ) = —^J { , 


( 2 ) 


where P = total breaking strength of the briquette and S = its sectional 
area. 

For the three forms of briquette shown in Figs. 358, 359, and 360 the 
R 

values of —, from eq. (1), are 1.22, 2.04, and 2.12, and the values of the 
^ 0 

p 

average stress r = are, from eq. (2), 1.14, 1.52, and 1.54, respectively. 






TESTING OF CEMENT. 


437 



Fig. 358.—Showing the Distribution of Stress in the Author’s Form. 



Fig. 359.—Showing the Distribution of Stress in the German Form. 



Fig. 360.—Showing the Distribution of Stress in the Standard English and American 

Form. 















438 


THE MATERIALS OF CONSTRUCTION. 


The last of these forms (Fig. 3G0) is the standard form employed in 
England and America, and is that recommended by the Committee of 
the American Society of Civil Engineers. The second (Fig. 359) is the 
standard form employed on the continent of Europe, and is commonly 
spoken of as the “ German standard.” The first (Fig. 358) is a form 
devised by the author to give a more even distribution of stress across the 
minimum section. An extended series of tests by the St. Louis Water 
Department shows results on neat Portland cement over 25 per cent greater 
on briquettes of the form shown in Fig. 358 than was obtained on exactly 
similar briquettes of the common American form shown in Fig. 360.* 
These higher results are partly due to the improved form of clips shown 
in Fig. 363. ' ' 

322. The Form of the Moulds. —It is customary to use single moulds, 

though multiple or gang moulds are often 

jj used where great numbers of briquettes are 
, ^ t° be made. In either case they should 
be made in two parts, as shown in Fig. 361, 
so as to be easily removed after the samples 
have set without danger of breaking the 
test-specimens. The parts may be held 
together by a spring, by clamps, or by a latch. They should always be 
oiled or soaped before using, to prevent the cement from adhering to 
them. 

Where the English system of measures is used it is now common to 
make the minimum cross-section of the briquette 1 inch square. It has been 
thought that the strength varied with the size of the section, as is appar¬ 
ently proved by the results plotted in Fig. 362, but in all probability this 
variation can now be explained by the greater inequality in the distribution 
of the tensile stress over the larger cross-sections. At least it seems fair to 
assume this to be the case until it has been disproved. 

323. The Clips—Their Bearings and Mountings. —Next in importance 
to the form of the briquette is the character of the clip by means of which 
the briquette is broken. The essential features of perfect clips are: 

1. They must grasp the briquette by a hard-cushion bearing on four 
symmetrical flat surfaces. 

2. They must be freely suspended from a pivot bearing, so as to turn 
without friction while under stress. 

3. They must be so rigid that they will not spread appreciably when 
subjected to their maximum load. 

The first requirement is necessary in order to avoid crushing the 


* If we use the subscripts a and b to distinguish the forms in Figs. 358 and 360 
respectively, we have, since R a = R b , 1.14r 0 = 1.54r 6 , or r a = 1.35r fe . That is to say, 
the form shown in Fig. 358 should be 35# stronger than that shown in Fig. 360. 



Fig. 361. 




















TESTING OF CEMENT. 


439 


briquette by the concentration of the load on a line or on a few points. 
Very hard rubber pieces should be dovetailed into the metal clips at th& 
bearing-surfaces, and allowed to project a little beyond the metal. 

When the second requirement is satisfied it is advisable to use an adjust¬ 
ing frame for placing the clips symmetrically on the briquette. 



Fig. 362.—Apparent Varying Tensile Strength of Cement for Different Areas of Cross- 
section of Briquette. (Grant and Whittemore, Engr. News, Dec. 14, 1893, p. 468.) 


All these demands are well satisfied in the form of clip and adjusting- 
frame shown in Fig. 363, which were devised by the author to be used with 
his new form of briquette (Fig. 358).* 

These clips are suspended from a steel point, the same as iii the 
German (Michaelis) machine. The hard-rubber (gutta-percha) pieces R 
bear directly on the tangent surfaces of the briquette, and they are brought 
to a symmetrical position (after the briquette is placed) by means of the 
adjusting-frame, which is set over the screw-heads at toj:> and over the 
raised guides at bottom and then slipped downwards to a bearing. The 
screw-clips at bottom are then turned, when both the briquette-clips are 
held rigidly against the adjusting-frame and in their true position. The 
movable clip is then screwed down to a hard bearing on the briquette, and 
the adjusting-frame removed. It might, however, remain on throughout 
the test if preferred, and in fact it could be permanently attached to the 
rear sides of the clips. 

* Both the moulds and the clips with their adjusting-frame are made by Malm & 
Co., instrument-makers, St. Louis, Mo. 
































440 THE MATERIALS OF CONSTRUCTION. 

These clips, used on briquettes of the form shown in Fig. 356, greatly 
increase the breaking strength of neat Portland cement. 



Fig. 363. —The Author’s Form of Clip and Adjusting-frame. To be used with the form 

of briquette shown in Fig. 356. 

324. The Testing-machine.—On the Continent Michaelis’ machine, shown 
in Fig. 364, is almost universally employed. The leverage is 50 to 1, and 
the load is imposed by means of small shot which escapes from a reservoir 
into the weight-pan. The dropping of this pan when the specimen breaks 
shuts off the flow of shot. The pan is then weighed, and its weight, multi¬ 
plied by 50, (this may be done in the graduation of the scales) gives the 
strength of the briquette. 

A very neat modification of this machine is that made by the Fairbanks 
Scale Co. and shown in Fig. 365. It is entirely self-contained and dis¬ 
penses with both the auxiliary reservoir and frame and the weighing-scales. 
The shot-pan is moved from the end of the weighing-lever and hung from 






































TESTING OF CEMENT. 


441 


the hook at the left, and a weight-hook hung in its place on the weighing- 
beam. The poise is then moved out on this beam, its extreme movement 
corresponding to a load of 200 pounds. For greater loads “ 200-pound ” 
weights are placed on the weight-hook and the poise moved out again to 
balance. In both the machines the load comes on gradually and without 



Fig. 364.—Standard Form of German Cement-testing Machine for Tension Tests. 



Fig. 365.—The Fairbanks Cement-testing Machine. 


shock by the flow of the shot, which is automatically shut off by the drop¬ 
ping of the beam, and the rate of imposition of the load can be regulated 
by varying the size of the gate. The tightening-screw P is first turned till 
the weighing-beam moves to its highest limit, and then any further amount 
to put an initial stress in the specimen short of rupture, after which the 
































































442 


THE MATERIALS OF CONSTRUCTION. 


free movement of the weighing-beam is sufficient to break the specimen 
without any further turning of the tightening-screw. The clips contain 
adjustable bearings intended to prevent the breaking of the briquettes in 
.the clips. 



Fig. 366.—Effect of Varying the Rate of Loading on the Tensile Strength of Neat 
Portland-cement Briquettes. (Faija, in Trans. Inst. C. E., vol. 75.) 


600 


400 


0 








<ONn 

'_ 





Or 

C/-\ 



fji 


$ 

N 

_ 

7AYS 

< 

2=d 

- 0 


— 


- c 

' iC 

as - 


MON. 

7T — 



§ 


< 

Aft 

AT^A 


WO/V7 

£ 



>-- 





— < 

Co c 



/C: 

asO 

\G£? 

DAY£ 


- - 

> 

>- — 

—<j 

H - 






I 











PTi 


POL 

'A/O 

S P 

CP 

WAY 

UTO 



0 000 400 OOO OOO 

Fig. 367.—Effect on Tensile Strength of Rate of Applying Load. 

Chf. Engvs ., 1895, p. 2951.) 


(Wheeler, Rep. 


The machines shown in Figs. 368 and 369 are made by Messrs. Riehle 
Bros, and by Tinius Olsen, respectively, both of Philadelphia. They both 
require the imposition of the load by hand; but as this is through a screw- 
gear and is very slowly applied, there would seem to be no appreciable un¬ 
steadiness in it. The beam is kept in balance at the same time by the same 
attendant, by moving out the poise till rupture occurs. Evidently the 
speed here is entirely under the control of the operator, and both these 
machines give entire satisfaction. 































































TESTING OF CEMENT. 


443 


In all these testing-machines the grips or clips are swivelled and 
mounted in such a way as to allow of a free universal movement, or adjust¬ 
ment of these to the specimen. 



Fig. 368. —Rielile Cement-testing Machine. 

Fig. 370 shows the construction of a cement-testing machine designed 
and used by Prof. J. M. Porter.* 

“ The load is applied by water flowing into a tank suspended from the 
long arm of a very sensitive 15-to-l lever. The weight of the lever and 
tank is counterbalanced by an adjustable weight shown on the left. Water 
is admitted to the tank from a large reservoir on the roof under a practi¬ 
cally constant head of 90ft., so that there is no sensible variation of pressure 
in the stream admitted through a carefully fitted gate-valve in the supply- 
pipe. The position of this valve at “ on,” “ off,” and all intermediate points 
is shown by an index attached to the stem of the valve and registering on a 

*The following description by the iuventor is taken from the Engineering News of 
March 5. 1896. 























444 


TEE MATERIALS OF CONSTRUCTION. 


dial marked off with the number of pounds per minute applied to the 
specimen as determined and verified by previous experiment. 

“ AY hen the briquettes break, the lever drops a few inches, then the 
plunger at the right end of the lever enters the pneumatic stop, and the 
lever & and tank are gradually brought to rest. During the fall of the tank, 
and before it comes to rest, a chain attached to the end of the valve- 
stem in the tank is brought into tension and arrests the descent of the 



Fig. 369.—Olsen Cement-testing Machine. 


valve before its seat stops descending. The opening of this valve allows 
the contents of the tank to be quickly discharged into a hopper placed 
upon the floor, and is then carried off through a waste-pipe to the sewer. 
As soon as the tank has discharged its contents, the weight ou the left end 
of the lever brings the lever and tank into the position shown in the illus¬ 
tration, the valve taking its seat during this movement, and the machine is 
ready for another break. The actual load can be applied at from 0 to 80 
lbs. per minute, thus giving an increase of stress of from 0 to 1200 lbs. 
























































































































































TESTING OF CEMENT 


445 


per minute. The speed generally used is 400 lbs. per minute, and with 
the valve set for this speed the needle-beam will float every time within 
\ second of the proper time. 

“ The stress on the specimen is measured by a poise travelling on a gradu¬ 
ated scale-beam, which can be read by means of a vernier to 1 lb. and can 



be moved automatically or by hand at the wish of the operator. The auto¬ 
matic movement is accomplished by the following-described device: 

“ The horizontal disk and its engaged friction-wheel are driven continu¬ 
ously by the pulley placed at the lower end of the vertical shaft and belted 
to overhead shafting. This friction-wheel is feathered to a sleeve that runs 






































































































































446 


THE MATERIALS OF CONSTRUCTION. 


loose on its shaft and carries a coned clutch that is nominally disengaged 
from its cone, which is also feathered to the shaft, and can be moved 
slightly longitudinally on the shaft into contact with the clutch by the 
action of the vertical lever, 

“ When the needle-beam rises, it makes contact through a vertical pin in 
the top of the frame, which completes an electric circuit and sends a cur¬ 
rent through the electromagnet and causes it to attract its armature at the 
lower end of the vertical lever, which moving to the right engages the fric¬ 
tion-clutch and causes the shaft to revolve. This shaft operates the 
sprocket-wheel and chain which draw out the poise on the scale-beam until 
the needle-beam drops, breaking the electric circuit. Breaking the elec- 
trie circuit releases the armature and allows the friction-clutch to disen¬ 
gage, and the poise comes to rest. The friction-wheel may be set at a 
greater or less distance from the centre of the disk by turning the capstan- 
head nut, and the chain is overhauled faster or slower, causing the poise to 
move accordingly. If desired, the poise may be operated by the hand- 
wheel without interfering with the automatic device other than cutting out 
the circuit. The chain is attached to the poise in line with the three 
knife-edges of the scale-beam” hence the tension in the chain has no ten¬ 
dency to lift up or pull down the poise. This point is often overlooked 
in designing this detail, not only in cement machines but in testing-ma¬ 
chines in general. The writer [Prof Porter] has a cement machine in 
which the error due to this cause is over 15 lbs. 

“ This machine as described has been in almost constant use for eigh¬ 
teen months and has given entire satisfaction. The operator has simply to 
place the briquette in the clips, open the supply-valve, wait until the bri¬ 
quette breaks, and then note the reading on the scale-beam. The objection 
to this machine is the space it occupies, requiring a floor-area of 7 X 2 ft., 
and the necessity of a constant head of water.” 

325. Importance of an Exact Central Position in the Clips.—It was shown 
in Art. 26 that if h — width of specimen and a — eccentricity of load¬ 
ing, the percentage of increase in the stress from this cause is given by the 

0 Cl 

fraction —. Thus if a cement briquette 1 inch thick be placed in the clips 

0.01 inch out of centre, its strength will be reduced by 6 per cent. This 
assumes perfect freedom of motion of the clips at the surfaces of contact, 
which they do not have. Experiments made at the Massachusetts Institute of 
Technology * have shown that a displacement of inch decreased the ten¬ 
sile strength by from 15 to 20 per cent (see Fig. 371). 

326. Compression Tests of Cement have not been common in America, 
though long practised in Europe. The excellent relation indicated in Fig. 
337, p. 419, between the tensile and the compressive strength of Portland- 


* Trans. Am. Soc. Meek. Engrs., vol. ix. p. 181. 





TESTING OF CEMENT. 


447 


cement mortar (1 C. to 3 S.) would seem to show that both tensile and com¬ 
pressive tests are not required, and American engineers have always acted 
on this assumption. 

The French Commission recommend compression tests, however, in addi¬ 
tion to the tension tests, but they do not advise the making of separate test- 
specimens. With the form of briquette shown in Figs. 355 and 356 the line 
of rupture is definitely fixed (with very few breaks outside the grooved sec¬ 
tion), and hence the two halves of the broken briquette will be nearly equal to 
each other and to all other broken parts. These ends are then to be tested 



W/t/o/v £cc£/zrm/ry 

Fig. 371.—Showing Effect of Eccentric Position of Briquette in Clips. (Assoc. Eng. Soc., 

vol. vii. p. 207). 

by crushing, the force to be applied normally to its bed, and the sum of the test 
loads on the two ends of one briquette to be the crushing strength of that 
specimen. In the absence of such broken briquettes to serve for this test, 
cylinders of the same area and height are to be made up and tested. 

Since this height is but 22 mm., while the diameter of the equal cylinder 
is 45 mm. (Fig. 355), the specimen has a height of but one half its lateral 
dimension, and hence the compressive strength of such a form of specimen 
is 20 per cent greater than that of a cubical form as shown in Art. 22, Fig. 17. 
The broken briquettes are chosen to avoid making up additional specimens, 
and also because this insures identical material for both the tension and 
the compression tests. For instituting a comparison with the compressive 
tests on otner material, where the cubical form has been almost universallv 
used, the correction coefficient of 0.83 can be employed, as stated above, 
or else cubical specimens can be prepared and tested. 

It ; s of course necessary to prepare all compressive-test specimens with 
care, by reducing the two bearing-surfaces to true planes. It would also be 
wise to provide a universal joint back of one of the bearing-plates.* 

* See method employed at the Massachusetts lustitute of Technology, Am. Soc, 
Mech. Engrs ., vol. ix. p. 172. 















448 


THE MATERIALS OF CONSTRUCTION. 


In America compression tests of cement are made on the universal test¬ 
ing-machines so common in this country. In Europe many special machines 
are made for this purpose, one of the most recent of which is shown in Fig. 
372. Here the load is indicated by the position of the radial arm moving 



Fig. 372.—Machine for Making Tests of Cement in Compression. (Manufactured by 

Amsler-Laffon & Son, Sckaffbauseu, Switzerland.) 

over the graduated arc, the actual movement of the upper head being thus 
multiplied a known number of times. As this movement is resisted by a 
powerful helical spring, when this spring has been standardized its compres¬ 
sion is a true index of the load. 

327. Cross-bending Tests of Cement have been advocated occasionally, 
but they have not come into general use anywhere. The French Commission 















































































































TESTING OF CEMENT. 


449 


e undertaken to standardize this test. They recommend a specimen 
o inches (120 mm ) long and 0.8 inch (20 mm.) scpiare in cross-section, 
and they show how this specimen may be broken on the Michaelis machine, 
Fig. 3G4, by attaching the centre-bearing, upward-pulling stirrup to the 
small hook at the left end of the lower lever. 

M. Durand-Claye has shown by very extended series of tests in tension 
and in cross-bending, on identical samples of neat Portland cement, that 
the average ratio of the modulus of rupture in cross-bending to the tensile 
strength, as determined upon standard forms of briquettes, is 1.92 at 7 days 
and 1.8G for 28 days, or an average of 1.89.* This relation was found to 
subsist between averages made up from the means of the three tests in each 
set of six, in both tension and cross-bending. The mean error of a single 
test at 28 days was found to be 2.10 per cent for the tension tests and 2.13 
per cent for the tests in cross-bending, thus showing that the two methods of 
testing were equally accordant. 

It would seem, therefore, that tests in cross-bending may be employed 
with assurance as a means of determining both relative and absolute values 
of cements and cement-mortars, their principal disadvantage lying in the fact 
that there are few records extant with which tc compare the results of such 
tests. 

The principal recommendation for the use of transverse tests would seem 
to lie in the economy of a testing outfit. It has been estimated that a 
suitable machine for testing cement transversely could be constructed for 
about $12, while a set of moulds for sixteen prisms would cost not to exceed 
$3, or if these latter be made of cast iron the cost need not exceed $5 per 
set of twelve after the patterns are made.f 

It is further claimed that since all transverse breaks are fair, while with 
the forms of briquettes and clips hitherto used in America nearly fifty per 
cent of the breaks occur outside of the minimum section, the results of 
transverse tests must be more reliable. If, however, a form of briquette 
and clip can be devised which will always give fair breaks, this claim of 
advantage will no longer stand. There seems to be now in this country 
no inclination to change from tension to transverse tests of cement. 

328. Standard Tests to Determine the Adhesion of Cement-mortars to 
Various Substances.—While the tensile strength of briquettes shows the 
cohesion of the mortar, it has been found by experiment that its adhesion 
either to other mortars or to the same mixture which has already hardened, 
or to brick or stone or metal, is very much less than its cohesion. It is 
important, therefore, to have a standard test of adhesion, as well as of 

* Messrs. Abbott and Morrison, in tlieir thesis published in Engineering News, Dec. 
14, 1893, show that for neat cement this ratio was 1.8 on prisms one inch square and 
broken on a span of four inches. 

f See Engineering News, vol. xxx. p. 469, where complete detail drawings are 
given of both the machine and of the moulds. 





450 


TEE MATERIALS OF CONSTRUCTION. 


strength. Because tests of this kind are comparatively new, no general 
custom has been established in America on the subject; but the following 
recommendations have been made by the French Commission: 

(1) For tests of adhesion of cements and cement-mortars use will be 
made of a special form of briquette, moulded in two parts, these two parts. 

consisting of the two materials whose adhe¬ 
sion is to be tested, provided both can be 
moulded, or containing between them a 
prism of the solid body to which the adhe¬ 
sion of the mortar is to be determined The 
form of this briquette, as modified for Eng¬ 
lish units, with one square inch of area on 
the surface of adhesion, is shown in Fig*. 
373. This mould is formed in two parts,, 
and is used to form in succession the two^ 
halves of the complete briquette. 

(2) To compare the force of adhesion of 
different cements to a given material, nor - 
mat adhesion-hlocks will be prepared as fol¬ 
lows: Use for these always one kind of 
standard Portland cement which has passed 
a sieve of eighty meshes to the linear inch, 

mixed with the standard sand No. 3 (see 
Fig. 373. —Form of Briquette for . , n1N , . ,, ,. £ » 

. . r rV * Art. 317) m the proportion ot one or cement 

A(ilicsiou 1/6SL or (Jement its ' i f 

adopted by the French Commis- to tw0 ot sand. These normal adhesion- 
sion and adapted to English blocks will be moulded in the form of one 
Units. half of the briquette shown in Fig. 373.* 

It will be ganged with 9$ of water and rammed into the mould. At the 
end of 24 hours in air it will be placed in fresh water for a period of at 
least twenty-eight days. When it is to be used, it will first be dried and its 
adhesion-surface polished with emery-paper. 

(3) The cement to be tested for adhesion with these standard blocks 
prepared as above will be mixed as a normal plastic mortar, one of cement 
to three of sand (see Art. 316), which will be introduced into the mould 
with a trowel, this mould now being placed with a normal adhesion-block at 
the bottom in place of the movable metallic disk. The mould will remain 
upon this completed block until it is ready for testing, and the block will 
be allowed to harden either in air or water, and for such period as the test, 
requires. It is recommended that the number of tests, the periods of time,, 
the methods of hardening, and the recording of the results should comply 
with the conditions given for tension tests in Art. 319. 



* The detail drawings of these moulds are given in the Fr. Com. Iiep., vol. iv. p. 284* 



















TESTING OF CEMENT. 


451 


(4) To compare the force of adhesion of a given cement to different mate - 
Tials. For this purpose the test-specimens will be prepared as described 
above, except that in place of the normal adhesion-blocks similar blocks of 
the various materials to be tested will be prepared and allowed to harden, 
provided these are such as can be moulded in this manner. If such mate¬ 
rials are solid, small disks, about three-eighths of an inch thick, will be pre¬ 
pared, and these will be used in the bottom of the mould in place of the 
metallic disk, the adhesion-block to be completed by using neat Portland- 
cement mortar. After this has hardened the briquette will be completed 
by making the other half of a standard plastic mortar, one cement to three 
of sand, using the particular kind of cement whose adhesion to these 
various substances is to be tested. 

If the normal plastic mortar is not used in adhesion tests, a full descrip¬ 
tion of its composition should be indicated on the records. 

These adhesion-briquettes to be broken on a standard tension-testing 
machine, using the regular tension-clips. 

329. Normal Variations in Volume of Cement-mortars in Air and in 
Water.—From elaborate tests on the swelling and shrinking of cement-mor¬ 
tars hardening in air and under water made at the Massachusetts Institute 
of Technology, Boston, and by Professor Bauschinger at Munich, it may be 
stated: 

1. Cement-mortar hardening in air shrinks almost uniformly for a period 
of more than three months, the linear shrinkage in that time being, for neat 
cement, from 0.12 to 0.34 of one per cent, and for cement-mortar, one of 
■cement to one of sand, from 0.08 to 0.17 of one per cent. The change in 
volume is of course three times the above percentages. 

2. Cement-mortars hardening under water increase in linear dimen¬ 
sions from 0.04 to 0.25 of one per cent in three months for neat cement, and 
from 0.00 to 0.08 of one per cent for a mortar composed of one part cement 
to one of sand; the volumetric expansion being three times these 
amounts. 

Professor Bauschinger found for nine German Portland cements, neat, 
an expansion, when hardened under water, of 0.05 of one per cent in sixteen 
weeks; Mr. Grant found for English Portland cement an expansion of 0.08 
•of one per cent in three months, this latter figure agreeing with the average 
results of the tests made on eight kinds of Portland cement at the Massa¬ 
chusetts Institute.* 

For mortars composed of one part of cement to three of sand the varia¬ 
tions in volume are very much less than those given for mortars of equal 
parts of sand and cement. 


* See progress reports of committee of the Am. Soc. C. E. on the compressive strength 
of cements, vol. xvn. p. 215, and vol. xvm. p. 264. 








452 


THE MATERIALS OF CONSTRUCTION. 


330. Recommendations of the French Commission for Testing Perma¬ 
nency of Volume. —Tests of permanency of volume may be of two general classes— 
cold and hot. 

Cold Tests will be made upon thin cakes of neat-cement paste made up on glass, 
about six inches in diameter and f inch thick at the centre, with thin edges, and 
placed immediately in water or in air, along with the briquettes which are hardening 
in these two media. These cakes to be examined at periods of 7 days, 28 days, 3 
months, 6 months, 1 year, 2 years, etc., corresponding to the like periods for the tests 
of strength. 

To measure the amount of the linear change of volume of neat cement immersed 
in cold water, a small cement form, 32 inches long and T inch square in section, may 
be moulded and placed vertically in a glass tube 1 inch in diameter filled with water. 
The expansion would be indicated by tlie movement of the long arm of a lever over 
a graduated scale, which is actuated by a pin embedded in the upper end of tlio 
specimen when made.* 

Evidently it may require years to assure one of the permanency of volume, or 
soundness, of a cement by the use of the cold-water and air test. 

Hot Tests to be made on cylinders of neat cement IT inches (30 mm.) high and 
IT inches in diameter, made up and left in metal moulds composed of sheet metal 0.02 
inch (0.5 mm.) thick (No. 25 gauge). This mould to be entirely severed on one 



Fig. 374. —Apparatus for Testing Permanency of Volume of Cement. (Recommended 

by the French Commission.) 

element, and to have soldered to it on the opposite side two arms, six inches long, 
forming an angle with each other as shown in Fig. 374. The decreasing distance be¬ 
tween the extremities of these arms to be a measure of the swelling of "the cement. 

These moulds to be immersed in cold water as soon as filled, and allowed to set 
for 24 hours, or for a shorter period if it is a quick-setting cement. The mould will 
then be placed on a grating in a vessel of water and its temperature raised to the 
boiling-point in from 15 to 30 minutes. This temperature is to be maintained for 
six hours, when the water will be allowed to cool down before removing the speci¬ 
men for remeasuring the distance between the six-inch arms. 

This hot test not to be applied to natural cements, or to any cement which sets 
very rapidly. 

The consistency of the cement used in both the hot and the cold tests to be of the 
normal consistency described in Art. 31G. 

331. The Permeability of Cement-mortar is often a very important mat¬ 
ter, as in the case of reservoir wells and linings, and often in foundation- 
walls placed below the level of the ground-water. Neat cement-mortar 
is absolutely impervious when it has hardened and has not cracked, 
and so also is a mixture of one to one, or even of two of sand to one of 


* Sec Fig. 25, p. 302, vol. i, Report of the French Commissiou, 1895. 














TESTING OF CEMENT. 


453 



cement, by weight, if well mixed. The normal mixture of three of sand 
to one of cement may also be made practically impervious with the most 
thorough mixing of the dry ingredients 
and a compacting of the mortar by hard 
ramming. 

Professor Tetmajer has used the appara¬ 
tus shown in Fig. 375 to obtain a modulus of 
permeability. Here a cylinder of the mortar 
is made and allowed to harden under water 
for a specified time. It is then mounted 
in the apparatus by means of annular rubber- 
cushion or packing disks, and the water let 
on below under a known pressure. The 
permeability of the mortar is indicated by 
the rate at which the water passes the disk 
and rises in the glass tube above, which 
is graduated to cubic centimeters. The W 
author has also used this apparatus with 
satisfactory results, a convenient pressure 
to use being that of the city water-mains. 

The French Commission 
recommend a standard per¬ 
meability test as follows: Fj T 3<5.—Tetmajers Apparatus 

J _ tor Jesting the Permeability or 

(I) The permeability of Cement - mortar. ( Communica- 
cement-mortars will be indi- twns > v °b VI -^ 
cated by the number of liters of water passing per hour 
through a cubical block of 7 cm. (say 2f- inches) on a side,, 
under the following conditions. 

The water will be brought to the top face of the specimen,, 
laid edgewise (what was the horizontal plane in the forma¬ 
tion of the cube now becoming a vertical plane), through a 
glass tube, 35 mm. internal diameter and about 4 or 5 inches 
high, which is sealed to the top face of the cube by neat 
cement-mortar as shown in Fig. 37G. A rubber tube con- 
Ap- nects the upper end of the glass tube with the reservoir 



placed at a height (from the surface of the water of immer- 


Fig. 376.- 
paratus for 

Permeubi H t y s ^ ou sur ^ ace the water in the reservoir) of 4 inches, 

of Cement-mor- 40 inches, or 400 inches (0.1 m., 1.0 m., or 10.0 m.). 
tar. (Recom- Before beginning the experiment the cube of mortar to 
mended by the p e immersed in water for 48 hours, and during the test the 
French Com- p] oc p j s to remain immersed to prevent the formation of an 
mission.) impervious coating on the outside from the evaporation of 

the exuding water. 

The volume of water passing will be given for the standard periods of 










































































































454 


THE MATERIALS OF CONSTRUCTION. 


24 hours, 7 days, 28 days, and 3 months. For very porous mortar a 
shorter period than 24 hours may be employed, and at the same time the 
head of water used must be stated. 

Tests will be made on three similar specimens, the mean of the two most 
accordant results to be used. 

(2) The normal test of permeability will be made on cubes made up of 
normal plastic mortar (3 sand to 1 cement, by weight) as described in Art. 
319, and the specimen cubes must harden in water under the normal con¬ 
ditions for 28 days before testing. 

For tests on other mixtures, and for other periods of hardening, they 
recommend that mixtures of 2 sand to 1 cement, and 5 sand to 1 cement, by 
weight, and hardening periods of I days, 28 days, and 3 months be chosen. 

In all cases the composition, age, and conditions of hardening must be 
stated, as well as the amount of water passed and the pressure-head used. 

332. Tests for the Decomposing Action of Sea-water.—As a result of the 
porosity of cement-mortars and concretes and of the resulting action of sea¬ 
water on the interior of the mass, producing therein certain changes partly 
by solution and partly by the formation of new' chemical compounds, cement- 
mortars and concretes are often disintegrated when subjected to the action of 
sea-water. The French Commission have.carefully studied this question, 
and have recommended the following test, which they regard as of value in 
determining the comparative resistance of cement to this action: 

(1) Standard tension briquettes of normal plastic mortar (one cement to three, of 
sand) will be made, and after 24 hours in air will be placed in sea-water which is to 
be renewed every two days during the first week, and every week thereafter. During 
the first week the volume of this sea-water to be at least four times that of the bri¬ 
quettes immersed in it. 

An equal number of duplicate briquettes to be exposed in a similar manner to the 
action of fresh water. Tension tests on these duplicate briquettes to be made at the 
standard periods of 28 days, 3 months, 6 months, 1 year, etc., and the effect of the 
sea-water to be shown by a comparison of the results. 

(2) Filtration tests will be made on specimens having a cubical form, as described 
in Art. 331, and to be exposed to the action of sea-water both in the bath and in the 
filtration reservoir there described. The head will be 4 inches, 40 inches, or 400 
inches, according to the permeability of the specimen. Two sets of duplicate test- 
specimens will be subjected to this test, one having hardened in sea-water and the 
other having hardened in air for the several standard periods chosen. 

A third duplicate set of exactly similar cubical blocks to be preserved and hard¬ 
ened in fresh water for the same periods of time. 

In the absence of actual sea-water, artificial sea-water will be prepared with the 
following formula: 


Chloride of sodium (NaCl).. 30 g. 

Sulphate of magnesia, crystallized (Mg0S0 3 ,7H 2 0). 5 

Chloride of magnesium, crystallized (MgCl,6H a O) . 6 

Sulphate of lime, hydrated <Ca0S0 3 ,2H 2 0). 1.5 

Bicarbonate of potassium (K0H 2 0,2C0 2 ). 0.2 

Distilled water. 1000 


All the above cubes to be superficially examined and tested in compression at the 
standard periods chosen. 

The following observations will be taken: 








TESTING OF CEMENT. 


455 


(а) The comparative appearance of the specimen subjected to the several kinds 
of treatment. 

(б) The tensile strength of the two sets of briquettes which had hardened in 
salt and in fresh water. 

(e) The compressive strength of the three sets of cubical blocks which had hard¬ 
ened in salt water and in air, and which had been subjected to the filtration tests, 
and the blocks which had hardened in fresh water. 

( d ) Chemical composition of the cubical blocks subjected to the several kinds of 
treatment. 

For other compositions, mortars composed of one cement to two of sand, and one 
cement to five of sand, to be chosen and tested at the standard periods of 7 days, 28 
days, 3 months, etc. 


CHAPTER XXII. 


TESTS OF THE STRENGTH OF STONE AND BRICK. 

TESTS OF STONE. 

333. Tests of the Strength of Stone Limited to the Crushing Test.— 

Since stone can readily be prepared for crushing tests, these have been 
almost exclusively employed in determining its strength. In view of the data 
obtained from comparative tests of cement in tension and compression shown 
in Fig. 337, p. 419, it might be inferred that the crushing test would show 
also the relative strength in tension. Since failure in crushing is a failure 
by shearing, it might be supposed that the true relative shearing strength 
would also be shown by the compression test. When stone fails in cross¬ 
bending it breaks first on the tension side of the beam, and hence this is a 
failure in tension, and therefore the crushing test has been thought to give 
correct relative values of cross-breaking strength. 

These assumptions prove not to be correct, however, as has been very 
conclusively shown by Bauschinger in volumes x, xvn, and xix of his 
Communications, where the results of tests on more than a thousand speci¬ 
mens of building-stones of the various kinds found in Bavaria are given. 
These tests were made in compression, in tension, in cross-bending, and in 
shearing, and no fixed relation can be given to these several kinds of 
strength. Probably this is largely due to the fact that stones are not amor¬ 
phous bodies, but are usually either sedimentary or crystalline or both, with 
definite planes of cleavage and of weakness. Since stone is used, however, 
almost exclusively in compression, it is usually considered sufficient to test 
its strength in compression only. 

The conditions to be fulfilled in the crushing test of stone are sufficiently 
elucidated in Chapters III and XVI. While the test-specimens should have 
heights greater than their least lateral dimensions, yet in order to make the 
results comparable with those hitherto obtained and recorded it is necessary 
to continue to make these tests on cubical forms. 

TESTS OF PAVING-BitICK. 

334. Kinds of Tests Required.—The use of brick for the wearing sur¬ 
face of street-pavements is now so universal that this new product, “ vitri- 

456 






TESTS OF THE STRENGTH OF STONE AND BRICK. 


457 


fied paving-brick,” has become one of the most important of the materials 
employed by the civil engineer. Since appearances in this material are 
entirely untrustworthy, and since these products vary greatly not only as. 
between the output of different manufacturers, but also as between different 
kilns of the same factory or even in different parts of the same kiln, a 
thorough system of mechanical tests to determine the probable wearing 
qualities is absolutely essential. To develop these qualities four tests are 
now commonly accepted as essential, namely *. 

1. Cross-breaking. 

2. Crushing. 

3. Impact (the rattler test). 

4. Absorption. 

335. The Cross-breaking Test.—This is made on single whole bricks by 
setting them edgewise on two rounded knife-edge bearings about 7 inches 
apart and loading them at the centre. In order to insure a true bearing of 
the knife-edges the brick should be ground to true parallel surfaces, or else 
the lower bearings should be rounded longitudinally sufficiently to prevent 
a twisting or torsional action. The cross-breaking modulus of rupture is. 
found by applying the formula 

3 Wl 
* ~ 2bh*' 

336. The Crushing Test is usually made on a half-brick, set edgewise,, 
and one or both of the ends of the brick previously used in the cross-break¬ 
ing test may be used. As these faces are very rough in paving-brick (from 
their having been reduced to a semi-plastic condition in the kilns, these 
being the bearing-surfaces), it is impossible to make fair crushing tests on 
these forms without grinding them to true parallel planes. This can readily 
be done on a regular stone- or marble-grinding table operated by steam- 
power, such being available in all large cities. When this is done they may 
be bedded on single thicknesses of tar-board, or placed directly between 
steel plates in the testing-machine. Great care must be exercised to place 
the specimen centrally in the machine, and to see that the bearing-plates 
fit evenly upon the specimen. One of these plates should have a spherical 
base to make it adjustable and so insure an even and true bearing on the 
test-specimen. The specimen should fail all at once, with a loud report, 
with little or no previous spalling. The load must be increased very slowly 
and uniformly, and the weighing-beam automatically balanced if practicable. 

337. The Rattler Test.—Formerly this test was made as an abrasion 
test by using a great quantity of small castings. The author has long in¬ 
sisted that this test should partake of the character of an impact test, and 
this view now generally prevails. Paving-brick are broken to pieces in 
service rather than worn or ground down, and the property of resilience 
is the one sought rather than hardness. The standardizing of this test 

" See Recommendations of a Committee of the National Association of Brick Manu¬ 
facturers, in Art. 338. 





458 


THE MATERIALS OF CONSTRUCTION. 


has proved a difficult task, but it has been fairly accomplished by Mr. 
F. F. Harrington, a former student of the author’s, now in charge of the 
Testing Laboratory of the Board of Public Improvements of the City of 
St. Louis. Mr. Harrington’s rattler is a cast-iron* barrel, polygonal in form 
and having fifteen staves, similar to that shown in Fig. 377. Its length 
is 42 inches and its diameter is 24 inches, and it revolves on trunnions at 



Fig. 377.—Rattler for Testing Paving-brick.* 


Fig. 



378.—Rattler Test of Brick showing Maximum Impact-effect when the barrel 
has 15% of its volume filled with brick. (Harrington.) 


the ends. A movable cast-iron partition can be inserted on the inside so as 
to shorten the length of the part used to anv amount less than 42 inches. 


* Cast iron has proved a failure in this work. The sides should be of steel plates. 





































TESTS OF THE STRENGTH OF STONE AND BRICK. 


459 


It is operated by an electric motor which is also used for other purposes 
in the laboratory. 

Fig. 378 shows the results of placing different amounts of brick in the 
barrel. Evidently there would be a particular amount (percentage of 
volume) whicliwould give a maximum impact-effect. This proves to be 
15$. That is to say, when 15$ of the volume of the interior of the barrel 
is filled with brick, solid measure,* the impact-effect was a maximum, the 
barrel making 30 revolutions per minute. This quantity was then adopted 
as the quantity of material always to use. 



Fig. 379.—Showing the Effects of Time in the Rattler Test of Paving-brick 

(Harrington.) 


In Figs. 379 and 380 the effects of time and speed are shown when the 
standard quantity of brick (15$) was in the barrel. Since the 60-minute 
curve gave an even 20$ loss at 30 revolutions per minute, this being 
regarded as about the proper amount, this product, of 1800 revolutions, was 

chosen. 

The effect of the length of the barrel is shown in Fig. 381, all being 
filled to 15$ of the total volume. It will be seen that the length of the 

* This means that the total solid contents of the brick equals 15% of the volume 
of the barrel. 




















460 


THE MATERIALS OF CONSTRUCTION. 


barrel has no sensible influence on the tests, provided it is always filled to 
the same percentage of its volume. 

338. Standard Tests of Paving-brick.—As a result of these experimental 
tests, and of similar ones carried out by Prof. Edward Orton, Jr., of the Ohio 
State University, chairman, a committee of the National Association of 
Brick Manufacturers of America, appointed in Feb. 1896 reported,in Feb. 
1897, recommending the following tests as standard:* 

1. A rattler test, made in a cast-iron f rattler 28 inches in diameter and 
20 inches long, having fourteen flat sides with one-fourth-inch spaces inter¬ 
vening;. The rattler to be filled with 
a number of anv given kind of brick 
equalling in total volume 15 </ 0 of the 
volume of the rattler (requiring 1800 
cu. in. of brick volume, or from 20 
to 24 brick for this standard size). 
The rattler to be run 1800 revolu¬ 
tions at the rate of 30 revolutions 
per minute. In no case must a dif¬ 
ferent kind of brick or other material 
be used to make up the charge. 
Other sizes of rattler, from 26 inches 
to 30 inches diameter and other 
lengths, could be allowed, and the 
speed might vary between 24 and 
36 revolutions per minute. 

Two such tests on any given 
species of brick to constitute a 
standard rattler test, and the aver¬ 
age result to constitute the record. 
This result to be a given percentage 
of loss of weight in terms of the orig¬ 
inal weight. The individual bricks 
do not need to be identified in the 
two weighings in this test. 

2. A cross-breaking test (number 
of tests not stated) to be made as 
described in Art. 335, the lower knife-edges to be rounded to radii of 15 
inches longitudinally and ^ inch transversely. The span to be 6 inches. 

3. A crushing test as described in Art. 336, or with the undressed bear¬ 
ing surfaces embedded in plaster of paris. 

Tests 2 and 3, for strength, were not regarded by the committee as 
essential, but were made optional 

* The author, ou invitation, participated in the proceedings of this committee, 
f The sides should be made of steel plates. 



Fig. 380.—Showing the Effects of Various 
Speeds in the Rattler Test of Paving- 
brick (Harrington.) 




















TESTS OF TIIE STRENGTH OF STONE AND BRICK. 


461 


The absorption-test was condemned as misleading, inasmuch as no brick 
which could endure the proposed rattler test would ever absorb enough 
water to injure it; while if the test be used, a thoroughly vitrified (glassy) 
brick might be preferred to a semi-vitrified one because of its smaller 
absorption. 

It will thus be observed that the committee regarded the rattler test, as 
here proposed, as quite sufficient to determine the wearing and weathering 
qualities of paving-bricks. This test alone requires from 40 to 50 brick to 
be furnished, since it is to be made in duplicate. As a matter of conven- 




20 - 


22 " 


70% 


% 

«_;_ 



N -- 



’ 

& /7m mm = 24 , 
^ 2220222202 0 f m 

K l 2 TV /? 2 2/ 

W022S 22/0//72/0/VS 
/M20222222/ 27/722i 

02 2) . 

222A//2222^30~~ < 

V/T202/222/02=72% 

0 2 2 2 2 


/2 2 / 22 c 32 

Fig. 381.—Showing Effect of Length of Barrel in the Rattler Test of Paving-brick. 

(Harrington.) 


fence, therefore, the rattler should be made double, or so as to contain two 
apartments having the dimensions described above. 

The first effect observed in the rattler test is one of chipping on all 
edges. After these have rounded off somewhat the effect is more evenly 
distributed over the outer surface, but it still remains principally an impact 
action. The dust and small pieces fall through the spaces left between 
staves for this purpose, so that the rattler remains comparatively clear of 
debris. If absorption-tests are made, they should be made on bricks which 
have passed the rattler test, because their glazed surfaces are then broken, 
if not largely removed. 

Accordant results could not be obtained when different kinds of brick 
were put in the rattler at one time or when other materials, such as stone, 
granite, or cast-iron blocks, were employed; hence the requirement that 
the full complement of material in the rattler should consist of the brick 
tested.* 

* The author has long used six-pound cast-iron bricks with rounded edges in con¬ 
junction with granite blocks, the loss of the brick being found as compared with the 
loss of the granite. See Engr. Neics, Apr. 18, 1895. The city of Philadelphia has 
adopted this method, but omitting the granite blocks, and they find they can compare 
the results of different tests when run the same number of revolutions. The University 
of Illinois has adopted this test, but uses two sizes of cast-iron blocks, in equal propor¬ 
tion, these weighing one pound and eight pounds each. See Technograph , No. 12, U. of Ill. 
















CHAPTER XXIII. 


TESTS OF THE STRENGTH OF TIMBER. 

339. The Variable Strength of Timber.—As shown in Chapter XIII, 
sound timber of a given species varies in its strength from two general 
causes, its structure and its moisture condition. Neither of these sources 
of strength (or weakness) has hitherto received proper study and analysis, 
and hence the known variations in the strength of timber has been attrib¬ 
uted either to its inherent and undiscoverable variations, or to variations 
in the size of the sticks tested. Some of the most important conclusions 
to be drawn from the U. S. Timber Tests are: 

1. The strength of timber is about tioice as great when it is dry as ivheiv 
it is green or wet* 

2. The strength of a given species of timber at a given percentage of 
moisture is governed by the ratio of the summer (solid) to the spring (open) 
ivood, or in other ivords by its specific gravity or solidity. 

3. The strength per square inch of a large stick in every kind of test is 
fully equal to that of a smaller stick cut from it ivlien both are similarly 
proportioned and similarly free from faults. 

4. It is very highly probable that the strength of all kinds of wood-fibre 
of like structural arrangement (thus putting the oaks into a separate class) 
increases directly with the specific gravity (or weight per cubic foot) of the 
dry wood. (See a discussion of this subject in Chapter XXXII.j 

The moisture state is the great and governing cause of variation in 
strength. When reduced to the same moisture condition it may be said, as 
a result of about 40,000 tests of timber made by the author, that in crushing 
endwise 90 per cent of all tests fall within 25 per cent of the mean, and 
55 per cent of all tests fall within 10 per cent of the mean-value for that 
species, and this is about as much as can be said for other kinds of building 
materials when all have been subjected to a reasonable inspection. 

340. “ The United States Timber Tests/’ f so called, were inaugurated in 
1891 by Dr. B. E. Fernow, Chief of the Forestry Division of the U. S. 
Agricultural Department, and have been carried on with frequent inter¬ 
ruptions ever since. r ! hoy consist of a vprv complete series of investiga- 

* See the curve showing variation of strength with moisture in Chapter XXXII. 
f See Bulletins 6, 8, 10, 13, and others to be issued from time to time by the U. S. 
Agricultural Department, Forestry Division, and to be had on application to the chief of 
that division. 


462 




TESTS OF THE STRENGTH OF TIMBER. 


403 


tions into the habitat, conditions, and laws of growth, structure, strength) 
and other properties, seasoning, preservation, and decay, and finally the arti¬ 
ficial cultivation of the useful timbers of the United States. The great im¬ 
portance of the timber industry (being second only to that of agriculture in 
this country), and the universal absence of accurate (scientific) knowledge 
on these subjects, have seemed to warrant the undertaking and prosecution 
of this the greatest series of physical investigations ever carried out. The 
field-studies and the collection of the material have been done by Dr. 
Charles Mohr; the structural investigations have been made by Mr. Filibert 
Roth in Washington; and the mechanical tests have been made under the 
direction of the author in his testing laboratory at Washington University, 
St. Louis, Mo. The species examined and tested to date (December, 1896) 
are given in tabular form in Chapter XXXII. It there appears that there 
have been selected for these tests— 

1. Sixty-eight trees of Long-leaf Pine* from South Carolina, Alabama, 
Mississippi, Louisiana, and Texas. 

2. Twelve trees of Cuban Pine from South Carolina, Georgia, and Ala¬ 
bama. 

3. Twenty-two trees of Short-leaf Pine from Alabama, Missouri, Arkan¬ 
sas, and Texas. 

4. Thirty-two trees of Loblolly Pine from South Carolina, Georgia, Ala¬ 
bama, and Arkansas. 

5. Seventeen trees of White Pine from Michigan and Wisconsin. 

6. Eight trees of Red (Norway) Pine from Michigan and Wisconsin. 

7. Four trees of Spruce Pine from Alabama. 

8. Twenty trees of Bald Cypress from South Carolina, Mississippi, and 
Louisiana. 

9. Four trees of White Cedar from Mississippi. 

10. The test specimens of Douglas Spruce were not taken from selected 
trees, but were obtained from lumber shipments to the St. Louis markets. 

11-20. Eighty-three trees of ten species of Oak from Alabama, Missis¬ 
sippi, and Arkansas. 

21-27. Twenty-four trees of seven species of Hickory from Mississippi. 

28-29 Five trees of two species of Elm from Mississippi and Arkansas. 

30-31. Four trees of two species of Ash from Mississippi. 

32. Seven trees of Sweet Gum from Mississippi and Arkansas. 

Besides these a great many small trees were taken, from which disks were 
cut at frequent intervals, from butt to top, and sent to Washington for the 
physical and structural studies Complete field notes were taken, also, of 
the geographical position, the immediate surroundings as to forest growth, 
character of soil, moisture conditions, etc. The diameter of the stump, the 
age of the tree, and the distance to the first limb were also noted. 


* Sixteen of these were “ bled ” trees to determine the effects of “ boxing.” 






464 


THE MATERIALS OF CONSTRUCTION. 


All this material has come from the Southern States except the white and 
Norway pines. The trees have been selected and cut by Dr. Mohr; the logs 
cut from them were shipped to the author at St. Louis in car-load lots. 
Disks 8 inches long have been taken from all these trees, at a number of 
heights, and also from many trees of the same species too small for timber- 
test specimens, and sent to Mr. Roth at Washington. The logs have 
been cut into test-timbers in various ways as shown in Fig. 382. The 
largest forms are full-sized beams (from the 18-foot logs) and columns (from 
the 12-foot logs), the size depending on the size of the log. The intermedi- 
.ate forms are 4 inches square, the standard size of the “ small ” sticks. The 






Fig. 382.—Showing Methods of Sawing U. S. Timber Test Logs. 

smallest size is 2 inches square, which has been employed only in “ special 
investigations.” The form in No. 6 indicates that two or three large 
sticks are to be cut and tested to failure, from the uninjured portions of 
which are afterwards cut smaller sticks which are also tested for the pur¬ 
pose of comparing the strength of large and small sizes. Form No. 5 has 
been adopted as the standard method of cutting when only 4-inch 
sticks are taken. Only logs over 24 inches in diameter at the small end 
could furnish this entire system of sticks, smaller logs giving the five interior 
ones only. The logs are always laid out on their upper ends, taking the 
pith as the centre of the diagram regardless of how unsymmetrical this may 
























































TESTS OF THE STRENGTH OF TIMBER. 


465 


lie in the cross-section of the log. The logs are always 12 or 18 feet in 
length, and tiie 4-inch test-sticks are cut to C-foot lengths, thus getting 
two or three such lengths from each 4-inch stick shown in the log diagram. 

341. The Mechanical Tests.—As a rule the following tests have been 
applied to every 4-inch stick: 

1. Cross-bending. 

2. Crushing endwise of the grain. 

3. Crushing across the grain. 

4. Shearing along the grain. 

5. Tension. 

Since June 1895 no tests have been made in tension, as it was thought 
this kind of strength was so great as to remove it from the category of pos¬ 
sible methods of failure. It was thought timber would never fail in pure 
tension in practice. 

For each and every test a section of the stick about r 3 F inch thick is cut 
from near the point of failure, and used for determining the percentage of 
moisture as described in Art. 343. 

The test-sticks were subject to a system of inspection and rejection 
which it was thought would correspond to such a system in actual practice 
where the timber was to be used in structures where the parts are propor¬ 
tioned to their loads, and hence it is thought the average of all the results 
fairly corresponds to such an average strength in practice at similar stages 
of dryness. 

In order to make the results comparable it was of course necessary to 
reduce them all to equivalent values at a standard percentage of moisture. 
For all reductions made previous to May 189G this standard had been 15 per 
cent moisture, computed on the dry weight. After that date 12 per cent was 
chosen as better representing the condition of the roughly seasoned timber, 
whether in or out of doors. In a dry, heated building the moisture falls as 
low as 8 or 10 per cent. 

342. The Cross-bending Test on the 4-inch sticks is made on a small 
8000-lb. testing-machine designed by the author, shown in Fig. 301, page 
370, while the large beams are tested on the 100,000-lb. machine shown in 
Fig. 302, page 371. In both cases the loads are applied so as to produce a 
uniform rate of deflection (with the 4-inch sticks it is always at the rate of 

1 inch per minute, while with the larger sticks it is J inch per minute) in 
order to eliminate the time-effect, which is very large with timber especially 
under the higher loads. 

With the small sticks two central bearing-points are used, 12 inches 
apart, thus putting that length of stick under the maximum bending-stress, 
and so really testing 12 inches in length of the stick instead of about 1 or 

2 inches with a single bearing.* Of course in all cases the bearings are 

* This was done as the effect of a paper by Prof. J. Burkett Webb before the Am. 
Assoc. Adv. Science, Section D, at Rochester, N. Y., 1892. 





466 


THE MATERIALS OF CONSTRUCTION. 


spread over a considerable area by means of steel plates to prevent the de¬ 
struction of the fibres by crushing across the grain. With the large beams, 
an oak saddle some 30 inches long, of the full width of the beam, and 
rounded slightly on the bottom in a longitudinal direction, is used for the 
centre bearing under the knife-edge of the machine. 

The deflections of the small beams are measured by means of a microm¬ 
eter-screw bearing on the head of the power-screw, as shown in Fig. 301, 
while in the case of the large beams a thread was stretched (by a rubber band) 
along one or both sides from nails in the neutral plane above the end bear¬ 
ings, and readings taken on a scale tacked to the beam at the centre. The 
scale was nickel-plated and kept polished to act as a mirror, and the par¬ 
allax of the thread on the scale was obviated by bringing the thread and its 
image into coincidence when the readings were taken. The readings were 
made to 0.001 inch with the small beams and to 0.01 inch with the large 
beams. 

The formulae of reduction for strength, modulus of elasticity, and resil¬ 
ience were adapted to the particular method of test employed; but since the 
resilience in inch-pounds per cubic inch is different for the two cases (single 
and double bearings at centre), the larger results obtained with a double 
bearing have been reduced to their equivalent for a single bearing to make 
them all comparable with each other and with the results usually obtained, 
which would be with a single bearing. The resilience of a beam loaded at 
the centre, in inch-pounds per cubic inch, is from eq. 6, p. 84. 

m __ i_ r 

r ~ 18 E 

This is also the measure of the resilience of the outer ends of the beams 
tested with double bearings at the centre, while for the part between the two 
centre bearings, where the bending moment is uniform, it is, from eq. 10, 
p. 85. 


The / being the same in the two cases, namely, the “ apparent elastic 
limit” of the material, found by fixing a point of the bending-stress diagram 
where the rate of deformation is 50$ greater than at the origin, as explained 
in Art. 13, p. 18. 

The results obtained from each cross-bending test of timber, therefore, 
are: 

1. Modulus of strength at the “ apparent elastic limit.” 

2. Modulus of strength at rupture. 

3. Modulus of elasticity. 

4. Modulus of resilience, or springiness. 

When large beams have been tested to failure, two smaller (4-inch) beams 
6 feet long have been cut from the upper side of the larger beam at one end, 


TESTS OF THE STRENGTH OF TIMBER. 


467 


and two from the lower side at the other end, and these four small beams 
have been subjected to the same test to discover whether or not the ordinary 
formulae are correct, or, what is the same thing, to discover whether the same 
values of the moduli named above would be obtained from both sizes. All 
the tests which have been made of this kind go to show that when both sizes 
are equally free from faults this is true. This proves that the strength of 
large sizes may safely be computed from tests on smaller sizes, other things 
being equal. 

343. The Crushing-endwise Test.—For this test a section about 8 inches 
long of the uninjured portion of a 4-inch beam which had been tested in 
cross-bending, is taken by means of a circular cutting-off saw, and tested to 
failure in compression endwise. The stress-diagrams in this test are fairly 
indicated in Fig. 383. Failure occurs by a buckling down of the fibres as 
shown at B, Fig. 113, page 241. After this buckling action of the fibres 
across the entire section has occurred the strength of the specimen is only 
about 0.8 what it had been originally, as is shown in Figs. 29 and 383, 



Fig. 383.—Typical Stress-diagrams of Timber when subjected to Compression Endwise. 


this residual strength remaining about constant for largely increasing 
deformations. 

This is the most valuable and characteristic single test to which timber 
can be subjected. It is The only one in which a relatively large stick can be 
evenly and simultaneously tested to failure throughout its entire cross- 
section. It should be expected, therefore, to give more uniform results than 




























468 


THE MATERIALS OF CONSTRUCTION. 


any other, and such proves to be the case. It is also the simplest and easiest 
to make. For commercial purposes, therefore, this test alone would serve 
nearly every purpose, all the other various kinds of strength and stiffness 
being inferred from this one test. 

344. Crushing Across the Grain. —Since timber is very weak in crush¬ 
ing across the grain, as compared to crushing endwise, this is found to be 
one of the most common methods of failure in practice. It is common to 
rest a timber column on a sill of the same wood, and to design the column 
for its maximum working load, paying no attention to the utter inability of 
the sill to carry this load without crushing. Many failures of timber 
structures are due to this cause alone. 

As there is no definite point of failure in crushing across the grain, two 
limits of deformation have been arbitrarily chosen at which the load has 
been recorded, namely, at three per cent compression, as a working limit 
allowable, and at fifteen per cent compression , as an extreme limit, or as 
failure. The apparatus used to indicate these two limits, for heights (thick¬ 
nesses) of specimen from 2 inches to 4 inches, is shown in Fig. 292 and ex¬ 
plained in the text of Art. 282, p. 357. With such timber as oak, which 
has large medullary or pith rays, the crushing strength in a radial direction 
is greater than in a tangential direction. 

345. The Shearing Test. —This is intended to develop the strength of 
timber to resist shearing along the grain. This strength is very small in 
nearly all kinds of wood, and may be reduced almost to zero by seasoning 
checks. It is a very common method of failure in timber framework, and 
hence it is important to test for it. The apparatus used is illustrated and 
described in Art. 300, p. 386. 

346. The Tension Test. —The tensile strength of timber is so great (often 
over 30,000 lbs. per square inch) that it is difficult to make a fair test of 
timber in this way. Simple shouldering is out of the question, since the 
specimen shears out or the shoulders crush down. The author, after trying 
various methods, adopted the simple forms of specimens shown in Fig. 
113, p. 241. This figure does not show the reduction of the cross-section 
at the centre, which was done by cutting out two segments of circles on the 
two sides by a band-saw, these segments having about an 18-inch radius. 
The reduced section left at the centre of the specimen was about 3 inches 
by f inch, making something over a square inch of net section. These 
specimens were then gripped by flat, grooved, cast-iron wedges, in the 
100,000-lb. universal testing-machine, and pulled to failure. Of course 
nearly straight-grained timber must be used or the failure is partly or 
wholly one of shearing. This test was finally abandoned altogether, as it 
was assumed that timber would never fail in practice in this way. 

346^. Relation between Cross-breaking and Crushing-endwise Strength._• 

Mr. S. T. Neely, C.E., has discovered* a practical identity between the 


* See Circular No. 18, Forestry Division, U. S. Agricultural Department. 






TESTS OF THE STRENGTH OF TIMBER. 


468a 


cross-breaking strength at the true elastic limit (as obtained from the IT. S. 
Timber Test stress-diagrams) and the ultimate crushing strength. By 
referring to Fig. 383, p. 467, and also to Fig. 29, p. 51, and to the accom¬ 
panying tests, it will appear that the theory of a uniformly varying stress 
across the section of the beam will obtain practically up to the elastic limit; 
and since there is very little deformation in endwise compression until the 
ultimate strength is reached and the fibres are crushed down, as shown in Fig. 
113, p. 241, and since the tensile strength is always much greater than the 
compressive strength of timber, it should be expected that the stress on the 
extreme fibres of a beam would very nearly follow the theoretical law up to 
the failure of these fibres on the compression side. In other words, the 
elastic-limit strength of timber in cross-breaking is the same as the ultimate 
strength in compression endwise. And from what appears in the following 
article it results that we may say that the ultimate strength moduli of tim¬ 
ber beams , for permanent loads, may be taken as somewhat below the ulti¬ 
mate strength of the timber in compression endwise. 

346 b. Strength of Timber under Permanent Loads. —Timber is entirely 
different from other forms of building materials in this, that it constantly 



Fig. 383a.—Results of Time Tests on Dry Long-leaf Pine in Compression Endwise. 
The specimens marked Q were tested quickly, as in one or two minutes ; those 
marked T were loaded with various percentages of the breaking load of the two ad¬ 
jacent specimens, and this load was left on until failure occurred, and the time noted. 
The specimens were If in. square and 3 in. long. The points plotted are the averages 
of from three to six tests each. 

yields under heavy loads, and will finally fail under little more than one-half 
of the load required to break it on a short-time test, such as is ordinarily 
given in a testing-machine. Dr. R. H. Thurston reported a few time tests 



















































4 68b 


TIIE MATERIALS OF CONSTRUCTION. 


on small wooden beams, one inch square and four feet long, in the Transac¬ 
tions of the American Association for the Advancement of Science for 1881. 
He found that GO per cent of the breaking load would break the beams if left 
on some nine months. No other record of actual time tests on timber has been 
found, and, the U. S. Timber Investigations not having yet reached this 
subject in carrying out its elaborate program, the author lias made about 
seventy-five tests in crushing endwise for the purpose of filling this gap in 
our knowledge of timber, at least temporarily. His results are shown in 
Tig. 3S3«. Long-leaf yellow-pine sticks, forty inches long and two inches 
square, were cut from a single plank, and these had seasoned three years in 
the dry. Each stick was dressed down to about 1.5 inches square, and then 
cut into specimens three inches long, as indicated in the figure. The alter¬ 
nate specimens were tested in compression endwise in a testing-machine, as 
is ordinarily done, and the strength was found to be exceptionally uniform. 
The intervening specimens were then loaded in succession, with various per¬ 
centages of the average ultimate strength of the two adjoining specimens, 
and these loads left on until failure occurred. These time tests were made 
on a 30,000-pound screw-gear machine, like that shown in Fig. 258, p. 324, 
but the specimen was mounted in the machine upon a nest of four helical 
car-springs, which deformed about one inch under the loads imposed. This 
elastic base maintained a practically constant stress on the specimen even 
when slowly deforming under its load. Failure came suddenly in every 
case, and the time was usually noted within a small fraction of the total 
time of the test. The points plotted in Fig. 383rt are the average results of 
from three to six failures for each point.* The percentage of the ultimate 
short-time load which would finally crush a wooden column would be indi¬ 
cated by the position of the horizontal asymptote to this curve. It would 
doubtless fall somewhere between 50 and GO per cent of the ultimate short- 
time load. In other words, but little more than one-half the short-time 
ultimate load will cause a column to fail if left on permanently . Or, the 
ultimate strength of columns under permanent loads is only about one-half 
the ultimate strength of those same columns as determined by actual tests in 
a testing-machine. 

Since the compression-end wise test has been shown to be characteristic 
of the material and of all other kinds of strength, the above conclusion may 
be safely extended to all forms of stress, and hence we may safely state that 

the strength of timber under any kind of permanent load is only about one- 
half its strength as found by actual (short-time) tests. 

* To make these tests at widely different times strictly comparable the specimens 
should have been thoroughly coated with shellac varnish as soon as sawed to protect 
them from the varying moisture conditions of the atmosphere. This was not done in 
this instance. 








PART IV. 


THE MECHANICAL PROPERTIES OF THE MATERIALS OF 
CONSTRUCTION AS REVEALED BY ACTUAL TESTS. 


CHAPTER XXIV. 

THE STRENGTH OF CAST IRON. 

347. The Tensile Strength of Cast Iron varies from 15,000 to 35,000 lbs. 
per square inch, while ordinary foundry irons run from 18,000 to 22,000 
lbs.* This strength depends greatly on the size of the specimen as well as 
on the composition, and on its freedom from internal stress from a too 
rapid cooling. 

The general characteristics of cast iron when tested in tension are 
shown in Figs. 384 and 3S5. It will be seen that there is here no well- 



Fig. 384._Two Stress-diagrams of Cast Iron in Tension, each the average of eleven tests. 

Average tensile strength = 33,500 lbs. per square inch. (Wat. Ars. Rep. 1894.) 

defined “ elastic limit,” and if there be such a point it is very low in com¬ 
parison with the ultimate strength of the iron. The “ apparent elastic 
limit ” falls at about 15,000 lbs. per square inch (Fig. 385), or at about G0$ 

* When annealed in the malleable process its strength is raised to from 30,000 to 
50,000 ibs. per square inch, as shown in Chapter VII, p. 115. 


469 






























470 


THE MATERIALS OF CONSTRUCTION. 


of the ultimate strength, as is found to be the case with wrought iron and 
rolled steel. The permanent set at this point, while it looks large in Fig. 



Fig. 385.—Typical Stress-diagram of Cast Iron in Tension, with Location of the “Ap¬ 
parent Elastic Limit,” corresponding to a permanent set of 0.0001 of the length. 
{Wat. Ars. Tests , 1893.) 


385, is in reality only about of one per cent, or entirely inappreciable. 


It is safe to specify 25,000 lbs. tensile 
strength, if great strength is required. 
Mr. W. J. Keep has shown (Fig. 57, p. 96) 
that the cross -breaking strength is very 
largely a function of the size of the test- 
specimen. As tension-test specimens are 
usually cast about 1 in. to in. in diameter, 
this variation with size is not so important 
for tension-test purposes as it might appear 
from this diagram. The test-specimens are 
usually turned down, both at the gripped 
ends and on the reduced portion. Fig. 386 
shows a form of cast-iron test-specimen 
which is intended to dispense with turning- 
altogether; but even here it would be better 
to turn the gripped ends, to avoid all bend¬ 
ing stresses in the grips. 



Specimen which does not re¬ 


quire turning down. 














































THE STRENGTH OF CAST IRON. 


471 


TABLE XXIII.—COMPOSITION" AND STRENGTH OF HIGH-GRADE CAST IRONS 
MADE AT THE FOUNDRY AT THE U. S. ARSENAL AT WATERTOWN, MASS. 
TEST-SPECIMENS GROOVED. (Rep. 1894, p. 247.) 



o 

c$ 

0 

Carbon. 





5^' 

teg 

a.£ 


Composition of Charge. 

— 

3 

O 

T3 

a 

S 

Graphitic. 

Combined. 

Manganese. 

Silicon. 

i 

Sulphur. 

Phosphorus 

l 

<D 

£ V 
-+-> S- 

CO g 

a) El 
— o 1 

w 73 
c *~ 

CD CD 

Hardness. 

Muirkirk pig.35.3"1 

Old 8-inch shell.29.4 | 

Heads. 29.4 ! 

Scrap. 5.9 | 

cupola 

2.440 

0.900 

0.335 

1.137 

0.113 

0.572 

27,700 

16.07 

100 j 

Muirkirk pig. 35.3) 

Shell . 29.4 ] 

Heads. 29.4 ! 

Scrap . 5.9 j" 

100 ) 

Richmond pig No. 1. 10 

Richmond pig No. 2. 10 

Salisbury pig No. 4.. _— 15 

Salisbury pig No. 4, high 15 }■ 

do 

2.391 

0.960 

0.342 

1.081 

0.134 

0.505 

27,990 

15.20 

do 

2.487 

0.744 

0.461 

1.511 

0.118 

0.521 

31,980 

17.35 

Scrap .- • • 50 

100 J 

Salisbury pig No. 4. 27.5) 

Salisbury pig No. 4, high 27.5 | 
Scrap .-• • 45.0 j- 

do 

3.558 

0.608 

0.451 

1.212 

0.125 

0.655 

32,400 


100 J 

Salisbury pig No. 4, high 50 ) 

Salisbury pig No. 4. 50 ^ 

do 

2.279 

0.366 

0.353 

1.024 

0.118 

0.496 

34,453 


100 j 

Salisbury pig No. 4....... 33.3' 

Salisbury pig No. 4, high 11.1 
Soft pig .22.2 

air-furnace 

2.492 

0.739 

0.448 

1.231 

0.125 

0.816 

32,980 


Remelted pig. 33.3 

100 

Salisbury pig No. 4.--- 25 

Salisbury pig No. 4, high . 25 
Scrap. 50 

cupola 

2.393 

0.432 

0.450 

1.090 

0.140 

0.497 

31,110 


100 . 

Richmond pig No. 1. 11.1' 

Richmond pig No. 2. 11.1 

Salisbury pig No. 4. 16.7 

Salisbury pig No. 4, high 16.7 

do 

2.727 

0.299 

0.462 

1.363 

0.125 

0.477 

31,810 

15.83 

Scrap. 44.4 | 

- 1 

100 J 

Salisbury pig No. 4. 33.31 

Salisbury pig No. 4, high 11.1 , 
Soft pig. 22.2, 

air-furnace 

2.058 

0.778 

0.464 

1.560 

0.115 

0.619 

29,100 

20.47 

Remelted pig. 33.o 

joo J 

Salisbury pig No. 4 ..... 20 
Salisbury pig No. 4, high 20 
Soft pig . 20 

cuDola 

2.255 

0.731 

0.458 

1.297 

0.114 

0.491 

30,750 

18.00 

Scrap. 40 

100 . 

■ 


























































































































472 


THE MATERIALS OF CONSTRUCTION. 


COMPOSITION AND STRENGTH OF HIGH-GRADE CAST IRONS— continued. 




<D 

o 

a 

o 

Carbon. 





U 

= .5 

Composition of Charge. 

«W 

O 

a 

2 

Graphitic. 

Combined. 

Manganese. 

Silicon. 

' 

Sulphur. 

Phosphorus 

1 

t ® 
02 a 

05 X 

c - 

<u ® 

Richmond pig No. 1. 

Richmond pig No. 2. 

Salisbury pig No. 4. 

Salisbury pig No. 4, high 
Scrap. 

. 9.41 
9.4 
. 9 4 
9.4 
. 62.5 

cupola 

2.890 

0.458 

0.388 

1.645 

0.105 

0.487 

27,320 


100 









Muirkirk pig. 

Soft pig . 

. 38.51 
. 23.0 | 









Remelted pig.. 

. 38.5 j. 

air-furnace 

2.538 

0.979 

0.348 

1.316 

0.130 

0.642 

26,480 


100 J 









Salisbury pig No. 4 . 

Salisbury pig No 4, high 
Richmond pig No. 1 .... 

Richmond pig No. 2_ 

Soft pig . 

Remelted pig. 

9.61 
9.6 
. 9.6 

. 9.6 1 
. 23.i r 
. 38.5 

do 

2.770 

0.256 

0.470 

2.444 

0.110 

0.587 

28,010 


100 









Salisbury pig No. 4. 

Salisbury pig No. 4, high 

Richmond pig No. 1. 

Richmond pig No. 2 ... 

Soft pig. 

Remelted pig . 

. 8.31 
8.3 
8.3 
8.3 

20.0 j 

46.7 

do 

2.751 

0.357 

0.435 

1.908 

0.095 

0.420 

29,120 


100 









Salisbury pig No. 4... . 

Salisbury pig No. 4, high 

Soft pig .... . 

Remelted pig. 

33.31 
11.1 , 
22.2 ! 
33.3 f 

do 

2.538 

0.634 

0.355 

1.222 

0.090 

0.766 

28,520 


100 J 









Salisbury pig No. 4 . 

Salisbury pig No. 4, high 

Soft pig. 

Remelted pig.. 

33.31 
11.1 1 
22.2 1 
33.3 f 

j 

do 

2.577 

0.185 

0.361 

1.146 

0.115 

0.762 

31,020 


100 J 









Salisbury pig No. 4. 

Salisbury pig No. 4, high 

Soft pig. 

Remelted pig... 

33.31 

11.1 

22.2 

33.3 

do 

2.116 

0.640 

0.450 

1.419 

0.125 

0.678 

31,140 


100 









Salisbury pig No. 4 . 

Salisbury pig No. 4, high 
Scrap. 

22.5 | 
22.5 I 

cupola 

2.825 

0.479 

0.361 

1.062 

0.076 

0.238 

32,010 


100 j 









Salisbury pig No. 4 . 

Salisbury pig No. 4, high 

Richmond pig No. 1. 

Richmond pig No. 2. 

Soft pig. 

Remelted pig. 

8.31 
8.3 
8.3 
8.3 ' 
20.0 f 
46.7 j 

air-furnace 

2.481 

0.687 

0.454 

1.175 

# 

0.120 

0.673 

31,990 


100 J 











15.67 


11.08 


21.04 


17.44 


16.82 























































































THE STRENGTH OF CAST IRON. 


473 


The tensile strength and the relative hardness of various high-grade 
compositions are given in Table XXIII. 

348. The Compressive Strength of Cast Iron varies from 60,000 to 200,000 
pounds per square inch as shown in Fig. 55, p. 94. In Fig. 387 is shown a 



Fig. 387.—Average Results of Twenty-two Tests of Cast Iron in Compression, from 
B. L. 12-in. Rifle-mortars. {Wat. Ars. Rep. 1894, p. 105.) 


stress-diagram in compression, plotted from the average results from twenty- 
two tests of gun-iron. As these were made on specimens 10.5 inches long, 
having a sectional area of 1 sq. in., they all failed by triple flexure, or as 
columns, at an average value of 63,000 pounds per square inch, the actual 
crushing strength not having been found. (The tensile strength averaged 
33,500 pounds per square inch.) 

On the following page are given the results of all the available actual 
tests of full-size cast-iron columns. The strength per square inch is so low 
as to be very surprising. Instead of their warranting the use of the formula 


in common use for cast-iron columns, p 


80000 


1 + 


400 \d 


\2y 


it is found that the 


straight-line formula 


p = 34000 - 88- 
r r 


very closely fits the observed results. The remarkable discrepancy here 
shown between the crushing strength of small specimens of cast iron and 
that of the full-size members is doubtless due to hidden defects, but to such 
defects only as are likely always to be present. 


























474 


TIIE MATERIALS OF CONSTRUCTION. 


TABLE XXIIItf.—TESTS OF FULL-SIZE CAST-IRON COLUMNS. 

(Results of Tests made at Phceuixville, Pa., by New York Department of Buildings, 

1897.) 


Number 

Diam- 

Thick- 

Area in 

Length 

of 

ness of 

Square 

in Inches. 

Column. 

eter. 

Metal. 

Inches. 

(0 

I 

15" 

1" 

43.98 

1901" 

II 

15 

11 

49.03 

1901 

B2 

15 

H 

49.03 

1901 

B4 

15£ 

11- 

49.48 

1901 

(5) 

15 

111 

50.91 

1901 

(6) 

15 

1A 

51.52 

1901 

XVI 

8 

1 

21.99 

160 

XYII 

8 

1 3 

22.87 

160 

(7) 


1 9 

17.64 

120 

(8) 


1 fiT 

17.37 

120 

G4 

8 

f 

17.083 

147f 

F4 

9 

1 

25.133 

150 

D4 

12 

1 

34.588 

162 • 

C2 

14 

1 

40.841 

159f 


Actual 
Breaking 
Load per 
Squarelnch 
in Pounds. 

Radius of 
Gyration. 
» 

l 

r 

Breaking Load 
by Formula 

p = 34000 - 88- 
r 

30,830 

4.962 

38.341 

30,630 

27,126 

4.92 

38.668 

30.600 

24,434 

4.92 

38.668 

30,600 

25,182 

4.965 

38.318 

30,630 

35,435* 

4.936 

38.543 

30,610 

40,411 

4.899 

38.834 

30,580 

29,604 

2.50 

64.00 

28.370 

28,229 

2.486 

64.361 

28,340 

25,805 

1.786 

67.189 

28,090 

26,205 

1.805 

66.483 

28,150 

25,969 

2.741 

53.903 

29,260 

21,181 

2.872 

52.226 

29,410 

30,810 

3.906 

41.475 

30,350 

25,401 

4.609 

34.661 

30,950 


* Did not fail. 


RESULTS OF THE WATERTOWN ARSENAL TESTS. 
(Reports for 1887 and 1888.) 


Number 

of 

Column. 

Least 
Diameter 
in Inches. 

Approx¬ 
imate 
Thick¬ 
ness of 
Metal 
in Inches. 

Least 
Area in 
Square 
Inches. 

Length 
in Inches. 
(0 

Actual 
Breaking 
Load per 
Squarelnch 
in Pounds. 

Radius of 
Gyration. 

O') 

l 

r 

Breaking Load 
by Formula 

p = 34000 - 88- 
r 

990 

5.94 

0.98 

13.19 

131.6 

38.860 

2.11 

62 

28,540 

991 

5.90 

0.95 

12.27 

146.7 

43.350 

2.12 

69 

27,930 

992 

5.09 

0.85 

12.08 

150.0 

' 33,500 

1.77 

85 

26,520 

993 

4.74 

0.91 

11.75 

151.5 

26,840 

1.61 

94 

25,730 

994 

4.84 

0.91 

11.89 

128.6 

30,370 

1.63 

79 

27,050 

995 

4 87 

0.90 

11.80 

129.5 

29,830 

1.64 

79 

27,050 

996 

5.72 

0.66 

8.94 

127.6 

63,310 

2.12 

60 

28,720 

997 

2.97 

0.87 

5.19 

118.5 

31,850 

.97 

122 

23,270 

998 

3.00 

0.88 

5.27 

118.7 

29,990 

.97 

122 

23,270 

999 

3.00 

0.90 

5.50 

118.4 

33,350 

.97 

123 

23,180 

1000 

4.27 

1.00 

10.92 

84.6 

32,130 

1.31 

65 

28,280 

2000 

8.66 

1.36 

31.10 

157.0 

(25,720)* 

2.63 

60 

28,720 

2001 

7.87 

1.31 

26.33 

156.9 

(30,380)* 

2.37 

66 

28,160 

2002 

7.17 

1.16 

21.75 

156.9 

25,470 

2.16 

73 

27,540 

2003 

6.35 

1.13 

17.28 

156.9 

27,210 

1.89 

83 

26.650 

2004 

r 

5.57 

0.77- 

13.22 

156.4 

25,100 

1.71 

97 

25,360 


* Did not fail. 




















































THE STRENGTH OF CAST IRON. 


475 


349. The Cross-breaking Strength of Cast Iron is in general from one 
and one half to two and a quarter times its strength in tension on solid 
rectangular sections. The cause of this was discussed in Chapter V. In 
Fig. 389 are shown autographic stress- 
diagrams of four kinds of cast iron 
made on Keep’s standard test-bars 
i in. square and 12 in. long. They all 
showed the same strength of 450 lbs. 
at the centre, giving a computed mod¬ 
ulus of rupture of 64,800 pounds per 3^220 
square inch. It will be noted that 
their deformations under like loads 
are very different, thus giving rise to j#### 
enormous differences in their strength 
to resist shock. Thus their resistances 
to shock, as determined by the total 
areas of their stress-diagrams, are re- 300$? 
spectively 10.0, 21.5, 28.9, and 35.1 
inch-pounds per cubic inch.* These 
four tests were selected to show the 
necessity of observing the deflections 
as well as the loads, if resistance to 
shock is to be found. These diagrams 


22222 


0 




1 




4$ 

w 

Y 

A/ 


1 

k 

k 

$ 

V 


X 

§ 


5 

J 

. /A 

m 

A 




i F 
CY, 7 


m 





§ 

/V 








r 

i 






1 

1 


iff 






KJ 








! 








CVJ 








1/ 

f 







f 








1/72 

2/2 

?T/6 

'A/ 

//V 

M 

032 

A 


a/ 0.2 0.3 00 


o 

389.—Cross-breaking Autographic 
Stress-diagrams of Four Kinds of Cast 
Iron all haviug the Same Static Strength. 
(Keep, Tv. Am. Soc. Mech, Engrs ., vol. 
xvii, 1896.) 


also show that no great error is made /0222 
in the case of cast-iron if the area of 
the stress-diagram in cross-bending 
be assumed to be equal to one half the 
product of the breaking load into the 
total deflection. This is the common Fig. 
rule for cast iron. This half-product, 
divided by the volume or weight of 
the specimen between the supports, 
gives the shock-resisting modulus in 
inch-pounds per cubic inch or per pound of metal as the case may be, and 
is independent of the particular dimensions except that the smaller the cross- 
section the greater the strength-modulus , as is conclusively shown in Keep’s 
curves in Fig. 57, p. 96. Higher shock-resisting moduli will be obtained, 
therefore, on small (thin) sections than on large ones, and the only safe 
rule is to learn by trial what products to expect and to demand for given 
sizes of test-specimens and given grades of iron. (See Fig. 57, p. 96.) 

The committee of the American Society of Civil Engineers recommended 
(1896) a cross-breaking test of cast iron in which/ = 36,000 lbs. on a bar 


* These can be taken out per pound of metal if preferred. 




























476 


THE MATERIALS OF CONSTRUCTION. 


2 in. by 1 in. tested flatwise on a 24-in. base, with a deflection of 0.3 in. 
This corresponds to only inch-pounds per cubic inch. 

Mr. W. J. Keep has shown * that the 1-in. square bar gives more uniform 
results than any other size, because at this size the effects of varying per¬ 
centages of silicon are not appreciable, as is shown by Fig. 57, p. 96. In 
reducing the great number of tests on cast iron (some 500 in all) in sizes 
from i in. square to 4 in. square made for the Committee on Methods of 
Testing Materials of the American Society of Mechanical Engineers, Prof. 
Benjamin has found that the strength of all sizes of cast-iron bars can be 
related to that of the l-in.-square bar 12 in. long by the following formula: \ 


W = k 


b oM h i 


.89 


1.058 


( 1 ) 


where W = breaking load on the centre of the bar; 

1c — breaking load for a bar 1 in. square and 12 in. long; 
b = breadth of the bar in inches; 
h — height of the bar in inches; 

l = length of the bar in feet (multiples of 12 in., which is the length 
of the standard bar.) 


The theoretical relation is 



350. The Modulus of Elasticity of Cast Iron varies quite as much as its 
strength. In this respect it is anomalous, since for all rolled iron and steel 
the modulus of elasticity varies only about five per cent from its mean value 
for strength variations, in the case of steel, of several hundred per cent. 
There is probably a pretty definite relation between the strength of cast 
iron and its modulus of elasticity, the stronger iron having the higher 
modulus of elasticity, that is, it is stiller. At least this relation is very clearly 
shown in the curves in Fig. 55, p. 94. In general this modulus varies from 
10,000,000 to 30,000,000, but for ordinary foundry iron it may be taken at 
from 12,000,000 to 15,000,000, or about one half that of wrought iron and 
rolled steel. 

It may be well here to call attention again to a ready method of reading the 
modulus of elasticity from any of the tension- or compression-stress diagrams 
given in this book. Where the loads are given in pounds per square inch 
and the deformations in percentages, or proportionate parts of the lengthy 
then by observing where the tangent to the curve at the origin (or the curve 
itself if it is straight so far) crosses the ordinate which marks a deformation 
of 0.001, one has only to read the corresponding stress per square inch and 
multiply it by 1000. The modulus of elasticity of east iron is approxi¬ 
mately the same in tension, in compression, and in cross-bending. 


* Trans. Am. Soc. Mech. Engrs., vol. xvn. (1896) p. 681. 
f Ibid , p. 692. 







THE STRENGTH OF CAST IRON 


477 


351. Kirkaldy's Results. —In Table XXIV are given the results of 469 
tests of cast iron in each of the three ways, tension, compression, and cross¬ 
bending, all on identical material in each case. The averages of all are: 

Tensile strength . 25,000 lbs. per square inch 

Compressive strength.121,000 “ “ “ “ 

Cross-bending modulus.. 38,000 “ “ “ “ 

Quality-coefficient.6.5 in.-lbs. per cubic inch. 

The mere fact that these specimens were submitted to Mr. Kirkaldy for 
testing implies that the mixtures were better than are commonly used in 
foundry practice, and yet these average results could readily be reached in 
any good foundry. 

The small ratio of the cross-breaking modulus of rupture to the tensile 
strength, this having an average value of but 1.52, is due to the great depth 
(2 in.) of the transverse test-bar. The small value of the “ quality-coeffi¬ 
cient 99 is doubtless due to the same cause. Otherwise all these irons would 
be classed as comparatively brittle. 

As this “ quality-coefficient” was not taken out by Kirkaldy, and as it is 
probable that only breaking strength was specified, it is quite probable that 
high strength has been attained in this material at the expense of resilience 
or shock-resistance. The ratio of the cross-breaking modulus to that in 
tension is also lower with less flexibility. The modulus of elasticity was not 
computed for any of these tests, and as only the final deflections are given 
in the published report, it cannot now be computed from the tabular matter. 

352. Shrinkage Stresses. —The shrinkage of cast iron after it crystallizes 
is so great that, if not provided for, it causes excessive deformations which 
may develop very great stresses, even to rupture. The heavier or the thicker 
the casting the greater are these shrinkage stresses. These have been 
studied in the case of cast-iron guns, and one such analysis is shown in Fig. 
390. Here the metal was over 11 inches thick. The outer and inner 
surfaces cooled first, and the subsequent shrinkage of the interior put these 
parts in compression. But since the total internal stress across any diametral 
section must be zero, there being no external force acting, it follows that 
the total tensile stress must equal the total compressive stress. These were 
all found directly by cutting off a zone included between two transverse 
sections, and by cutting this up into a series of concentric rings as shown by 
the dashed lines in Fig. 390. Before cutting these, four diameters of each 
ring were carefully measured, and these same diameters were again measured 
after cutting out. An increase in mean diameter indicated an initial com¬ 
pression, and vice versa , the initial stresses being found from the equation 

f = \E, 

where f = stress in pounds per square inch; 

A = proportionate change in circumference; 

E — modulus of elasticity of the material. 





478 


THE MATERIALS OF CONSTRUCTION. 


TABLE XXIV.—SUMMARY OF RESULTS OF TESTS OX CAST IRON IN TENSION, 
COMPRESSION, AND CROSS-BENDING, ON IDENTICAL MATERIAL. 

From Kirkaldy’s Report, 1891 (Report T T). 


Total Number of Tests 
from One Foundry. 

Grade. 

Tension Strength in Pounds 
per Square Inch. 

Compression. 

Cross-bending. 

Strength in Pounds 

per Square Inch. 

__ 1 

Ultimate Deforma¬ 

tion, Per Cent. 

Computed Stress on 

Outer Fibre in 

Pounds per Square 

Inch. 

Ultimate Deflection 

in Inches. 

* Resistance to Shock 

or “Quality-factor” 

in Inch-pounds per 

Cubie Inch. 


Highest. 

32,821 

141,632 

6.65 

47.710 

.32 

8.84 

151 

Mean. 

26,165 

122,279 

9 26 

38,020 

.27 

5.94 


Lowest. 

16,250 

103,165 

12.20 

25,820 

.21 

3.14 


Highest.. 

27,614 

124,251 


37,390 

.32 

6.22 


Mean... 

24,303 

. 117,242 


33,840 

.26 

5.09 

74 






Lowest. 

19,311 

109,682 


27,260 

.21 

3.31 








Highest. 

28,740 

131,912 

13.30 

43,540 

.40 

1.00 

58 

Mean. 

24,148 

115,572 

9.98 

39,550 

.36 

8.24 


Lowest . 

17,698 

93,759 

4.45 

33,840 

.33 

6.46 


Highest. 

30,630 

137,165 

11.80 

46,460 

.33 

8.87 

46 

Mean. 

23,339 

105.918 

11.95 

36,190 

.36 

7.54 


Lowest. 

12,688 

66,363 

12.70 

34,240 

.38 

5.33 


Highest. 

29,782 

138,496 

10.40 

46,650 

.36 

9.72 

15 

Mean. ... 

22,727 

116 833 

10 66 

44.460 

35 

8 99 


Lowest. 

15,580 

GO 

OS 

cc 

© 

-> 

7.90 

42,860 

.32 

7.94 


Highest. 

26 040 

132 857 


36,100 

.28 

5.85 


Mean. 

23.925 

123,044 


34,760 

.26 

5.22 

15 





Lowest. 

22 711 

113,233 


31,360 

.24 

4.35 








Highest. 

25,708 

123.531 

9.20 

40.660 

.36 

8.47 

15 

Mean . 

23,129 

116,356 

9 12 

39,700 

.36 

8.27 


Lowest. 

17,617 

105,258 

7.35 

38,400 

.34 

7.56 


Highest. 

27.644 

122,708 

8.55 

39 290 

.39 

8.19 

13 

Mean . 

24,321 

116,538 

8.64 

32,780 

29 

5.50 


Lowest. 

19,188 

104,281 

7.00 

26,930 

.21 

3.27 


* This “ quality-coefficient ” is a measure of the resistance to shock, or it is the 
area of the stress-diagram in inch-pounds per cubic inch, found by multiplying the 













































































































































































THE STRENGTH OF CAST IRON. 


479 


SUMMARY OF RESULTS OF TESTS ON CAST IRON— Continued. 


Total Number of Tests 
from One Foundry. 

Grade, 

^ Tension Strength in Pounds 

per Square Inch. 

Compression. 

Cross-bending. 

Strength in Pounds 

per Square Inch. 

Ultimate Deforma¬ 

tion, Per Cent. 

Computed Stress on 

Outer Fibre in 

Pounds per Square 

Ultimate Deflection 

in Inches. 

♦Resistance to Shock 

or •‘Quality-factor' 11 

in Inch-pounds [per 

Cubic Inch. 


Highest. 

26,502 

175,950 

4.05 

54,140 

.45 

14.10 

13 

Mean. 

21,711 

123,336 

5.49 

40,750 

.34 

8,02 


Lowest. 

16,090 

103,859 

6.45 

27,070 

23 

| 3.60 


Highest. 

25,176 

127,988 

7.55 

36,050 

.32 

6.68 

10 

Mean. 

24 298 

125,962 

7.03 

34,750 

.29 

5.83 


Lowest. 

23,511 

120,874 

6.40 

31,870 

.25 

4.61 


Highest. 

30,316 

136,266 

12.25 

40,460 

.30 

7.02 

10 

Mean. 

29,268 

133,682 

12.61 

38,020 

.27 

5.94 


Lowest... 

28,436 

129,524 

13.90 

34,080 

.21 

4.14 


Highest.... 

30,018 

130,145 

12 10 

39,550 

.34 

7.78 

10 

Mean .... . 

29,472 

127,714 

11 90 

38,400 

.32 

7.11 


Lowest. 

27,501 

122,155 

11.75 

37,050 

.29 

6.22 


Highest. 

28,416 

140,542 

6.60 

38,780 

.31 

6.96 

10 

Mean. 

27,763 

138,054 

6.54 

37,250 

.28 

6.03 


Lowest. 

26,851 

135,577 

6.60 

35,330 

.27 

5.52 


Highest. 

25,520 

127,703 

7.80 

34,960 

.32 

6 46 

10 

Mean. 

24,803 

121,593 

7.71 

33,020 

.28 

5.35 


Lowest. 

23,435 

110,405 

6.60 

30,190 

.26 

4.54 


Highest. 

28,518 

129,603 

• 9.10 

40 370 

.35 

8.18 

10 

Mean .. 

27 914 

126,701 

9.70 

38,060 

.32 

7.05 


Lowest. 

27,276 

124,415 

9.15 

35,470 

.26 

5.34 


Highest. 

33,616 

143 939 


46,990 

.41 

11.15 


Mean . 

29,202 

137,804 


43,490 

.39 

9.81 

o 






Lowest. 

19,046 

124,410 


43,490 

.31 

6.82 







breaking load by the final deflection and dividing by twice the volume of the bar. It 
was not computed by Kirkaldy. All these bars were 2 in. X 1 im X 36 in. long, tested 
•edgewise, the tension and compression specimens being cast on the same pattern. The 
great depth of these bars makes this quality-factor and also the modulus of rupture run 
low as compared to tests on thinner specimens. 












































































































































































480 


THE MATERIALS OF CONSTRUCTION. 


In this way the stress-diagrams shown in Fig. 390 were computed and 
drawn by the author from the data furnished in the original report. It 
indicates that the interior surface was under an initial compressive stress of 
some 7000 lbs. per square inch, the outer surface of some 13,500 lbs. per 
square inch; while the interior was under a tensile stress of some 2000 lbs. 
pev square inch. Evidently the tension and compression areas on these 
diagrams must equal each other. This is a very simple illustration of such 
shrinkage stresses, because of its simple ancT symmetrical form. In complex 
forms it would be impossible to study or predict the character of these 



Fig. 390. —Showing the Shrinkage Stresses in Cast-iron Cannon 11 in. thick. 

( Wat. Ars. Rep.) 

stresses. They are evidently less when all parts are made of approximately 
the same thickness. 

353. Strength of Cast Iron Increased by Shocks. —Mr. A. E. Outerbridge 

has shown* that castings which have been subjected to a great number of 
shocks or blows are from 10 to 15 per cent stronger under a static load and 
over 20 per cent stronger under impact than they are before receiving such 
treatment. He attributes this result to a sort of molecular rearrangement 
by which the cooling stresses are relieved. In other words, such treatment 
is equivalent to an annealing process.—This is probably a general fact and 
true for all kinds of castings, although this remains to be proved.f 

354. Strength of Malleable Cast Iron. —For the experimental results of 
tests of the strength of malleable cast iron see Art. 82, p. 114. 

355. Cast-iron Pipes and Columns. —In estimating the actual strength cf 
cast-iron pipes subjected to internal pressure, a great source of uncertainty 

* Trans Am. Inst. Min Enqrs Pittsburg Meeting, 1896. 

f Mr. Keep Las shown that this increase of strength is due to the smoothing action on 
the surface and not to any molecular change. Trans. Am. Soc. Mech. Engrs., vol. xix. 





































































Original Form. 



’V-S 


Examples of Cold-bending, Forging and Welding of Malleable Cast-iron 
Specimens, all being originally like tiie Undeformed One in the 
Centre of the Plate. 


(Berlin Testing 


Laboratory Communications, vol. iv, PI. III.) 



















THE STRENGTH OF CAST IRON 


481 


lies in the probable unequal thickness of the metal in the upper and lower 
sides when cast. There is a great tendency of the core to rise from the 
buoyancy of the liquid iron, and since no core, however strong, can be abso- 
lutely rigid, it must be assumed that it does always lift somewhat at the 
centre, however strongly it is held at the ends. As a matter of fact, the 
cores are not usually very rigid, so that such pipet are apt to be very unequal 
in thickness on the opposite sides, as shown in Fig. 391 . The regular bell- 
and-spigot water- and gas-pipes are now all cast vertically, and hence this 



Fig. 391. —Actual Section of an 8-in. Cast-iron Steam-pipe. (From The Locomotive, 

Oct., 1896.) 

danger is largely obviated, but flange-pipes, such as are used for steam 
purposes, are cast horizontally. Any great inequality in thickness can be 
found by rolling the pipe down inclined ways and noting the irregularity 
of motion 

Cast-iron columns, such as are used in buildings, are also cast horizon- 
tall}', and are subject to this same contingency. These may be bored to 
determine thickness, but pipes cannot be examined in this way. It is such 
undiscoverable faults as this which form the greatest objection to the use of 
cast iron for these purposes. For other defects in cast-iron columns see 
Plate III. 






















































































































































CHAPTER XXV. 


THE STRENGTH OF WROUGHT IRON. 

356. The Tensile Strength of wrought iron along the grain varies from 
45,000 to 55,000 pounds per square inch. It is greater in small rods and 
thin plates than in large bars and thick plates, the material remaining 
the same. This is shown in Fig. 392, where the same material has been 
rolled into bars from f in. to 2 in. in diameter, the tensile strength varying 
from 52,000 in the smaller to 47,500 pounds per square inch in the larger 
sizes. 

The Elastic Limit is more dependent on the thinness of the final 
section than on the tensile strength, as is well brought out in Fig. 392. Here 
the apparent elastic limit varies from 40,000 pounds per square inch in the 
f-in. rods to 23,000 pounds per square inch in the 2-in. rods, and is almost 
identical with the “yield-point.” This increase in the elastic limit with 
increased reduction in the rolls always occurs with both wrought iron and 
steel, but it is much more pronounced with wrought iron. The true elastic 
limit of wrought iron is nearly always much lower than the apparent 
elastic limit. In Fig. 392 it is found from 5000 to 7000 lbs. lower in every 
case. In. mild steel these two limits are almost identical. 

The Percentage of Elongation in 8 in. varies from 5$ to 25$ when tested 
in the direction of the fibres, depending on the quality of the material, the 
reduction of area averaging about 50$ more than the elongation. The elon¬ 
gations recorded in Fig. 392 were all taken on a length of 20 in., which 
somewhat reduces the percentage, especially for the smaller sections. 

357. The Tensile Strength across the Grain is always much less than 
along the grain in the case of wrought iron, while with steel there is no 
appreciable difference. Very few tests of wrought iron across the fibres 
are to be found on record, but the author has often observed in his own 
practice that it is very much less in this direction than parallel to the 
direction of rolling. In Prof. BauschingeFs Communications, vol. n, we 
find an elaborate study of this subject on wrought-iron boiler-plates from 
eight different sources, some of them having been taken from boilers which 
had exploded. From this report we have— 

1. From eight tensile tests along and eight across the grain, from an 
exploded boiler, the ratio of lateral to longitudinal strength was 0.74. 

482 


THE STRENGTH OF W ROUGH! IRON. 


483 


2. From a wrought-iron plate from another exploded boiler eight test- 



Fig. 392.—Stress-diagrams (in tension) of Wrought-iron Bars of varying Diameters, 
all rolled from the same Material. All Elongations measured on a Length of 20 in. 
The “ Apparent Elastic Limit ” falls from 2 % to 10# lower than the indicated “Elas¬ 
tic Limit in the original Report; it varies from 23,000 in the 2-in. to 40,000 lbs. in 
the 3-in. specimens ; and it marks a point where the permanent set is less than 0.0001 
of the length of the specimen. Each diagram is the average of from 3 to 6 tests. 
{Wat. Ars. Rep. 1838.) 

specimens were cut in each direction, giving a mean ratio of lateral to 
longitudinal strength of 0.71. 































































































484 


THE MATERIALS OF CONSTRUCTION. 


3. On six other new plates from as many different sources he obtained 
ratios of 0.76, 0.62, 0.92, 0.90, 0.76, and 0.83. 

The average value of all these is 0.78. 

In short, we may fairly affirm that the ultimate tensile strength of 
wrought iron transverse to the direction of the rolling is only about three 
fourths of its strength parallel to this direction.* 

The author is credibly informed that the best English Yorkshire 
(Lowmoor) iron plates are always rolled from “puddled lumps” 12 in. 
square, which correspond to muck-bars, these being piled so as to cross 
their grain, and in this way the final plates are nearly as strong transversely 
as they are longitudinally. It is claimed that for an ultimate strength of 
51,500 pounds per square inch, with an elongation of 16# longitudinally, 
it shows an ultimate strength of 45,000 pounds per square inch and an 
elongation of 12# transversely. As this material costs about four times 
as much as the best mild-steel plates, its use for all purposes where forging 
and welding are not required is rapidly declining. 

358. Tensile Strength of Wrought Iron as Affected by Pulling Speed and 
by Length of Reduced Section. —In Table XXV are given the results of a 
series of very careful tests to determine the effects of speed and of the length 
of the reduced section on the tensile strength of wrought iron. It will be 
observed that the ultimate strength is somewhat increased by very rapid 
testing, while the elongation and reduction are not appreciably affected by 
this average range of speed from 15 sec. to 8.5 min. The strength is also 
much greater for very short reduced sections than for longer ones. Similar 
results on steel bars are shown in Fig. 426. 

359. The Compressive Strength of Wrought Iron, like that of any of the 
ductile metals, must be regarded as the “apparent elastic limit” or “yield- 
point.” Here the material buckles out of shape, and if the specimen has 
appreciable length, failure at once follows. If this be allowed, then it may 
be seen at once, from Fig. 392, that the same puddle-ball, rolled to different 
sections, will show compressive strengths anywhere from 26,000 to 40,000 
lbs. per square inch. Since wrought-iron columns are built up of structural 
forms which have been rolled to thin sections, from to f in. in thickness, 
it follows that such material will have a “yield-point” or “apparent elastic 
limit” of from 30,000 to 40,000 lbs. per square inch. Since, also, the amount 
of reduction in the rolls has a less effect on the elastic limit of mild steel, it 
follows that the yield-point, and hence the compressive strength, of a 
wrought-iron column may be about equal to that of a steel member built 
up of similar sections, although the ultimate strength of tne steel in tension 
may be 25 per cent higher than that of the wrought iron. This variation 
of the compressive strength (yield-point) of wrougnt-iron columns with the 


* The author has been unable to find the data for plotting a stress-diagram of 
wrought iron across the grain. 





THE STRENGTH OF WROUGHT IRON 


485 


TABLE XXV.—TESTS OF WROUGHT IRON TO SHOW EFFECT OF SLOW AND 
OF RAPID FRACTURES ON SPECIMENS OF VARYING LENGTH. 

Sixteen specimens taken from the same bar of iron If in. square, all reduced to a 
diameter of 1.008 in. or to a sectional area of 0.80 sq. in. Specimens marked from A 
to P consecutively, as cut from the bar. (From U. S. Wat. Ars. Rep. 1887, p. 924.) 


Marks. 

uength. 

\ 

Elastic 
Limit per 
Square Inch. 

Ultimate 

Strength 

per 

Square Inch. 

Duration 

of 

Test. 

Gauged 

Length. 

Elonga¬ 
tion in 
Gauged 
Length. 

Contrac¬ 

tion. 

Final Load 
per 

Square Inch 
. on Rup¬ 
tured Sec¬ 
tion. 


Inches. 

Pounds. 

Pounds. 


Inches. 

Per cent. 

Per cent. 

Pounds. 

A 

Grooved 

• • « • 

57,200 

6 min. 



32.4 

72,090 

B 

Grooved 

• • • • 

59,250 

6 sec. 



32.4 


C 

0.80 

27,375 

49,380 

6 min. 



49.1 

71,260 

D 

0.80 

.... 

50,750 

8 sec. 



37.1 


E 

1.00 

28,500 

47,730 

10 min. 

1 

56.0 

47.6 

78,280 

F 

1.60 

• • • • 

49,130 

13 sec. 

1 

50.0 

46.2 


G 

2.40 

30,125 

47.980 

8 min. 

- 2 

39.0 

43.2 

61,680 

II 

2.40 

• • • • 

49,000 

14 sec. 

2 

41.5 

49.1 

• • • • 

I 

3.20 

29,625 

47,070 

10 min 

3 

39.0 

49.1 

77,150 

J 

3.20 

.... 

48,120 

15 sec. 

3 

36.0 

47.6 


K 

4.80 

29,875 

46,860 

10 min 

4 

32.0 

43.2 

70,260 

L 

4.80 

• • • • 

48,000 

18 sec. 

4 

32 8 

47.6 


M 

6.40 

29,750 

47,450 

9 min. 

6 

25.0 

49.1 

80,590 

N 

6.40 

• • • • 

48,250 

20 sec. 

6 

32.0 

47.6 


O 

8.00 

28,500 

45,650 

9 min. 

8 

25.9 

41.7 

66,950 

P 

8.00 

• • • • 

46,000 

30 sec. 

8 

25.9 

41.7 

• i • • 

Mean of slow tests = 

48,670 

8.5 min. 


36.1 

44.4 

73,500 

Mean of quick tests = 

49,810 

15.5 sec. 


36.4 

43.7 

• • • • 


thickness of the sections of which the member is composed accounts for a 
large portion of the disc^enancies found in the results of tests on wrought- 
iron commits in commercial sizes (see Fig. 297, p. 364). Thus Tetrnajer 
found for short columns composed of four angle-irons, 2.4 in X 2.4 in. X 
l in. in thickness, tne average strength of the wrought-iron columns was 
38,000 lbs. per square men of net section, while that of similar mild-steel 
columns was but 36,000 lbs. per square inch. The ultimate tensile strength 
of the wrought iron was 50,000 lbs. per square inch, while that of the 
steel was 61,000 lbs. per square inch. With angles 0.4 in. thick the steel 
columns had an ultimate strength of 37,500 lbs. per square inch, while the 
wrought-iron columns showed only 32,300 lbs.* With sections f in. thick 
and less, therefore, there is probably little difference between the strength of 
wrought-iron and soft-steel columns. 

360. The Shearing Strength of Wrought Iron. — The most elaborate 
investigation ever made on wrought iron, so far as the author is aware, was 
that made by Bauschinger and reported in vol. n of his Communications . 
He made several hundred tests of the shearing strength of wrought-iron 
plates from seven different sources, finding the shearing resistance in two 


* Communications, vol. iv. pp. 141, 149, and 155. 





























486 


THE MATERIALS OF CONSTRUCTION. 


directions on each of the three of the principal planes, as shown in Fig. 393. 
As there was a general agreement in the relative strength on these planes, only 
the averages of a portion of the tests are given in the diagram. In general, 
we may say that the shearing strength across the thickness of the plate, either 
with or across the grain, is about 80 per cent of the tensile strength, while 
if the external forces lie in the plane of the plate, and be applied on the 



Fig. 393.—Shearing Strength of Wrought Iron on the Six Principal Planes, as compared 
to its Tensile Strength. The numbers indicate the number of results averaged. 
The direction of rolling is indicated by the large arrow. (Bauschinger’s Communi¬ 
cations, vol. II.) 

planes of shear perpendicular to the plane of tile plate, the shearing strength 
is about the same as the tensile strength. The shearing resistance on a 
plane parallel to the plane of the plate is less than 45 per cent of the tensile 
strength. 

361. The Effects of Stressing Wrought Iron beyond its Elastic Limit is to 

raise this limit, and also to greatly increase the ultimate strength after a 
period of rest. Thus in Fig. 394 are shown the results of tests on three 
wrought-iron bars 3 in. x 1 in. Here the apparent elastic limit on the 
second test (computed on the original cross-section) is much greater than 
the original ultimate strength, and almost equal to the ultimate strength on 































































THE STRENGTH OF WROUGHT IRON. 


487 




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Fig. 394. —Wrougiit-iroa Bars, 3 in. by 1 in. retested, First test gave El. lim. — 30,000; 
ult. str. = 53,700; belong. = 16 on 100 in. Ends of broken bars retested and loads 
computed per sq. in. of original section. Second Elongation taken on 50 in. and per 
cent elongation computed on the new gauged length. {Rep. Wat. Ars. 1882.) 


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Fig. 395.—Increase in the Tensile Strength of Wrought Iron after having been Stressed 
to the Tensile Limit. Points plotted are averages from 5 to 15 tests each. {Rep. 
U. S. Test Board, 1881, vol. 1 . pp. Ill and 115.) 



















































































488 


THE MATERIALS OF CONSTRUCTION. 


the second test. After annealing, however, the material snowed a much 
lower elastic limit and ultimate strength than it had before it was stressed 
at all. Stretching the material somewhat beyond the elastic limit, but not 
to failure, would show less marked results. If little or no time is allowed 
to elapse between the tests, there is no permanent increase in the strength, 
but the rate of increase in strength with time after stretching to its tensile 
limit is well shown in Fig. 395. 

When any ductile metal is stressed beyond its normal elastic limit in 
either tension or compression it loses its perfect elasticity under the opposite 
Jcind of stress. Thus for wrought iron. Fig. 396, has been constructed by 



Fig. 396.—Showing that a small Permanent Set of Wrought Iron from either Ten¬ 
sion or Compression greatly reduces the Elastic Limit under the Opposite Stress. 
(Gray, in The Digest of Physical Tests , vol. i. p. 232 (1896).) 

plotting consecutively a series of autographic diagrams taken by Prof. Gray.* 
Although at first the permanent set given to the specimen* in tension was 
less than one per cent of its length, yet when this was relieved and a com¬ 
pressive stress applied it was shown that the specimen was no longer per¬ 
fectly elastic in compression, but gave a continuously curving stress-dia¬ 
gram. It was then compressed back to its original length, and a tensile 
stress applied, when it was found to be no longer perfectly elastic in tension. 
It was now permanently elongated about one per cent of its length, and the 
load removed and again imposed, and it was found that the specimen was 
now perfectly elastic in tension up to the limit of its previous loading and 
somewhat higher, but when it was now elongated 18 per cent it was no 


* Reported in The Digest of Physical Tests, vol. i. p. 206. 























































































THE STRENGTH OF WROUGHT IRON. 


489 


2QM 


/sm 


longer perfectly elastic in either tension or compression. Similar results 
are shown on steel in Figs. 43G and 437. 

362. The Strength of Wrought-iron Chains. —The hundreds of tests on 
wrought-iron chains given in the Report 
of the U. S. Test Board, 1881, vol. i, 
show that the ultimate strength of 
chains may be taken at 1.6 that of the 
iron from which the links are made. It 
also appears from these tests that open 
links are somewhat stronger than studded 
links, though the open-link chains take 
a permanent set earlier than the studded 
links. It is thought, however, that open- 
iink cables would foul more readily than 
the studded cables. The elastic proper¬ 
ties of open-link chains made of 1-in. 


/#m 


sm 


a 




,p. 


i 

i 


j 

mm 

. i 

-r 

1 

1 

n 1 

1 


<0 


i ! 

i i 
r • 

1 

'v J 




♦ * 

■ ; 
i i 

i i 

il 




^ 

:■ 

^ // 



i 

.1 1 

1 i 

1 1 



\ 


1 r~ 

i > 
i 1 

mpt 

mm. 

4Tf P 

l 

_it 

i i 

r /M 


and J-in. iron are shown in Fig. 397, 
where the tests have been carried to the 
proof-load only, this being such as to 
give to the chains a permanent set of 
about two per cent of their length. They 
now become perfectly elastic to 20,000 
and 15,000 lbs. respectively, and are also 
about five times more stiff, or rigid, than 
they were at first. All chains are im¬ 
proved by this treatment, while it also discovers any very poor welds the 
chain may have. 


0 00/ M2 

Fig. 397.—Proof Tests of Chains with 
Open Links. The 118-in. chain 
made of 1-in. iron, and the 90-in. 
chain of f-in. iron. ( Wat. Ars. 
Rep. 1894.) 
















CHAPTER XXVI. 


THE STRENGTH OF STEEL. 

356. The Tensile and the Compressive Strength of Steel of various per¬ 
centages of carbon are well shown in Figs. 399 to 404.* A study of these 



Fig. 398.—Compression and Tension Tests on Midvale Steel Ears. Compression tests 
on bars 1 in. diam. and 5 in. long, tension tests ou bars 0.56 in. diam. and 5 in. long. 
{Wat. Ars. Rep. 1889.) 


* In all these figures the loads are given in pounds per square inch, though this is not 
always so stated. 


490 





































THE STRENGTH OF STEEL. 


491 



of Carbon. Compression specimens 12 in. long and 1 in. in diam. = 33^, with flat 

ends. Tension specimens same diam. with a gauged Length of 30 in. All speci¬ 
mens turned from open-hearth steel bars 1£ in. in diam. ( Wat. Ars. Rep. 1886 and 
1887.) 












































































492 


TEE MATERIALS OF CONSTRUCTION. 


figures, all of which are typical and characteristic, will lead to the following 
conclusions: 



1. The tensile strength varies from 55,000 lbs. for 0.1 per cent carbon 
to 150,000 lbs. per square inch for 1.0 per cent carbon. 




































































































THE STRENGTH OF STEEL. 


493 


2. The “ apparent elastic limit ” is found between GO and 70 per cent 
of the ultimate strength. 

3. The “ apparent elastic limit ” in compression is practically the same- 
as that in tension. 



durance Tests on Rotating Shafting subjected to Reversals of Stress. Percentages 
of carbon and areas of the stress-diagrams in square inches are given on the curves. 
(Rep. Wat. Ars. 1894.) See Table XXXVb, p. 5415, for results of the endurance 
tests. 

4. The modulus of elasticity in compression is slightly greater than that 
in tension, and in both cases it is practically independent of the percentage 
of carbon and of the ultimate strength. 

5. The ultimate strength in compression is practically equal to the 
“ apparent elastic limit ” (Fig. 294, p. 360). 































































494 


THE MATERIALS OF CONSTRUCTION. 


6. In the mild and medium steels (carbon 0.2 to 0.6 per cent) there is 
a very decided drop in the stress-diagram after reaching the “ apparent 
elastic limit ” often as much as 5000 or 6000 lbs. per square inch. 



Fig 402. —Tension Stress-diagrams (incomplete) of Steel Bars used for Endurance 
Tests of Rotating Shafting. Average product of ultimate strength by percentage 
of elongation is 2,180,000. (Wat. Ars. Reps. 1889 and 1891.) 


7. The coefficient of expansion decreases with the increase in carbon, its 
average value being about 0.0000065 per degree F. (Fig. 294). 

8. The high carbon-steels are greatly softened, the tensile strength 
lowered, and the ductility increased by annealing (Fig. 404). 






































































THE STRENGTH OF STEEL. 


495 


357. The Effect of Thickness on the Mechanical Properties of Structural 
Steel. In digs. 406, 407, and 408 are shown the effect of thickness (bars 
and angles) on the mechanical properties of structural steel. Thus from 



Fig. 403.—Tension Tests of Steel Bars used for Endurance Tests of Rotating Shafting. 
{Wat. Ars. Rep. 1889 and 1891. Supplementary to Fig. 402.) 


Fig. 406, where the thickness ranges by eighths of an inch from § to J inch, 
we may see— 

1. The ultimate strength is nearly constant. 

2. The apparent elastic limit varies from 41,000 at f to 37,800 lbs. per 
square inch at the 2-in. thickness. 














































































496 


THE MATERIALS OF CONSTRUCTION. 



Fig. 404. —Tension Stress-diagrams of Three Grades of High-carbon steel. {Wat. Ars . 

Rep. 1894.) 


60,000 












\ 


5QPOO. 


/ 

7 





X 



/ 






] 

40,000 



















N 










54 









20,000 










1 









mo 




















PRO 



?T/i 

W7E 

ao 

VGAT 

0, 



0 JO .20 .30 


Fig. 405.—Autographic Stress-diagram of 
Rivet-steel in Tension, showing Effect 
of Removing the Load. (M. Dupuy, in 
An. d. Ponts et Chaussees, PI. I. 1895.) 


70.000 


50,000 


70,000 


30000 , 


1 

$4? 


• 

„ Av k 


2j27c 

i 

y^>» 



OA/^, 

r 

i ~ 



> ■-- A 

\ 

§ 

ft 



& 

I^T 




1 

1 

1— 



H 

-JMl 

70A/G 

JA/-8JA 

t 

o-< 

T/i/02 

> ———< 

V£5§ C 

i—- - 

^Am 

/ * n 

- - 

£1 _ 

/ v r-r/ 




Fig. 406. —Effect of Thickness on the 
Mechanical Properties of Acid Open- 
hearth Steel Angles. (Campbell’s 
Structural Steel , p. 202.) 





























































































THE STRENGTH OF STEEL. 


41)7 


3. The percentage of elongation in 8 in. is nearly constant. 

4. The reduction of area varies from 58 per cent at f in. to 50 per cent 
at | in. thickness. 

r rni , , • Elastic limit 

5. 1 he elastic ratio: xjlt i mate strength vanes from 68 per cent at f in. 
to G1.5 per cent at f in. thickness. 


moo 


■SO.OOO 


40,000 


moo 


moo 


7 




1 







* 

>. 

1 

077?./). 



r\ \< 

o 


1 




% 

'1 



I*' 

N, f\ 

OOf- J 


;pT 



'Wri 

’tr M 

rm 

4A4S, 

1044a 

'O 


20 


Fig. 407.—Effect of Thickness on 
the Mechanical Properties of Mild 
Steel, Natural and Annealed. 
(Campbell's Structural Steel.) 


00.000 


40 50.000 


30 m00 


50,000 


— 

' uir. 

u. _ 

4 A ft 

' OTR 

-A/G-ft 

' * 

7.iL_ 





-^ 

• S 

S’ 






'3- 


4U, 

V/c / 

{Af/r 

—%■ 

—^ 

“1 1 

3 -< 

'oA/of 

70// 


T 

. r ‘ 

'mm 

/tt . 

~<r<? o/ 
/// 

-mu 

c 0 



30 


_ 20 

ft # 

Fig. 408.— Effects of Thickness on Bessemer Steel 
Angles. Each point is the mean of fifty re¬ 
sults. (Campbell’s Structural Steel, p. 199.) 


From Fig. 409 it may be seen that the variation in ultimate strength and 
in the elastic limit for different thicknesses is much greater when the metal 
leaves the rolls at a dull-red heat. Here the thickness ranges from f in. to 
| in., and the elastic limit for normal rolling varies from about 50,000 lbs. 
per square inch at the f-in. thickness to 39,000 lbs. at a f-in. thickness. 
When leaving the rolls at a dull-red heat, however, the elastic limit for the 
£-in. thickness was 57,500 lbs., while for the f-in. thickness it was only 
42,000 lbs. per square inch. 

In general the apparent elastic limit rises as the thickness of section 
diminishes. Since wrought-iron and steel columns are built up from com¬ 
paratively thin sections of metal (generally from d to | in. in thickness), and 
/as the ultimate strength of these is dependent wholly on the apparent elastic 
limit, and not at all on the ultimate strength, it is necessary to evaluate this 
elastic limit for the particular thicknesses of sections used, rather than from 








































498 TEE MATERIALS OF CONSTRUCTION. 



Fig. 409.—Influence of Thickness on Mechanical Properties when the Percentage of 
Reduction in Rolling is constant, and when the Last Passage in the Rolls was at the 
Normal and at a Dull Red Heat respectively. (Campbell's Structural Steel.) 

Fig. 410. —Showing the Effect of finishing Three Grades of Open-hearth Steel Bars at a 
Low Red Heat. (Campbell’s Structural Steel , Table 70.) 



Fig. 411.—Showing Effect of Annealing Open-hearth Steel Bars 2 in. X f in. when 
Rolled Originally at a Normal and at a Low Red Heat. (Campbell’s Structural Steely 
p. 213.) 































































THE STRENGTH OF STEEL . 


499 


special test-bars, which are usually not less than § in. in thickness. (See 
Table XXV, p. 503, for the comparison between the results obtained on the 
preliminary f-in. billet test-specimen and those from the specimens cut from 
rolled bars and plates of various thicknesses from the same ingot.) 

The comparatively small variation in the elastic limit (and other proper¬ 
ties) shown in big. 408 is due to the fact that all were rolled from the same 
sized ingot, and thus the thinner sections had more work done upon them. 
\\ hen the proportionate reductions are the same in each case the differences 
are very much greater, as shown in Fig. 409. These differences almost 
wholly disappear on annealing, as shown by Fig. 407. 

358. Effects of Finishing at a Low Red Heat.— As shown by Figs. 409 
and 410, the effect of finishing at a low red heat is to somewhat increase 
the ultimate strength and the elongation, and to greatly increase the elastic 
limit. This last increase is as much as from 8 to 10 per cent. From Fig. 
411 it appears that while annealing lowers both ultimate strength and elastic 
















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Vs 






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• 












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JL - 


OAT 

f o: 

SPPA 

P/A/6 

sm 

wer/ 

y pfa 

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TPA 

2/LE 

st/?l 


/ PL'A 

1 SO, h 

V 


0.6 


0.5 


0.4 


0.3 


0.2 


60% 65% 


20 % 


85% 20% 55% 


Fig. 411 a. —Showing thejAbsence of any Law of Relationship between Shearing Strength 
and Tensile Strength of Steel Plates when the Shearing Strength is determined by 
Punching Tests. (Experiments made at Washington University by Messrs Condron, 
Harrington, and Norton. See a full account of these in Engr. Neics, vol. x xn 
(1894), p. 164.) 


limit, it does not appreciably increase the elongation, neither does it bring 
the “normal” and “dull red” specimens much nearer together in the 
matter of the elastic limit. It might fairly have been assumed that annealing 



































•500 


THE MATERIALS OF CONSTRUCTION. 


would have removed the effects of rolling at a low heat, as it always does the 
effects of cold working, but it has not done so in this instance., 

358a. Punching Tests of Steel Plates. —It has been claimed * that 
■structural steel may be tested by punching in place of the ordinary tension 
tests. This subject was very fully investigated at the Washington University 
Testing Laboratory, as the subject for a thesis, by Messrs. Harrington and 
Norton, in 1894, assisted by Mr. T. L. Condron, C.E., and it was concluded 
that no definite relationship could be established between the results of 
punching and of tension tests on steel plates of varying quality and thick¬ 
ness. The tests were made with autographic stress-diagrams of every test, 
and hundreds of tests made on steel plates of known chemical composition 
and tensile properties. Fig. 411 a is here given as one of many such studies 
made of the results, all going to show that the punching tests could not be 
employed as tests of acceptance under any set of specifications.f 

359. Effects of Quenching and of Annealing on Structural Steel. —It 
is not generally known that quenching from a bright cherry-red heat has a 



Fig. 412.—Average Effects of Quenching Soft Steel (0.10 C.) from a Dull Red Heat. 

Each point the mean of six tests. (Campbell’s Structural Steel, p. 52.) 

Fig. 413.—Effects of Quenching a Very Low Carbon (0.057 C.) Steel at Different Tem¬ 
peratures. (Campbells Structural Steel , p. 53.) 

marked effect on the softest grades of open-hearth, steel. That it has is 
shown by Figs. 412 and 413, where a steel having a normal tensile strength 

* By Alfred E. Hunt before the World’s Engineering Congress, Chicago, 1893. 
Trans. Am. Soc. Civ. Engrs., voi. xxx. p. 181. 

t See an illustrated article by Mr. Condron in Engr. News, vol. xxxit. p. 164. 




























THE STRENGTH OF STEEL. 


501 


of 48,500 lbs. per square inch (Fig. 412) is raised to 63,500 lbs. per square 
inch by quenching. The apparent elastic limit is raised from 32,000 to 
46,000 lbs. per square inch; the elongation is lowered from 32 to 20 per 
cent in 8 in.; and the reduction of area is raised 55 to 63 per cent.* This 
reveals also the difference between the elongation and the reduction of area 
as characteristics of steel. The highest grade of steel wire, having a 
strength of 200,000 lbs. per square inch and upward, and having an elonga¬ 
tion of but one or two per cent, will commonly show a reduction of area of 
over 60 per cent. That is, the stretch largely occurs at the necked-down 
portion only. The cold-bending test is a test of the reduction of area rather 
than of the elongation. In Fig. 413 the effects are shown of quenching soft 
open-hearth steel from various temperatures from a dull red to a bright red 
heat. These two figures both show that the softest steel is greatly changed 
by quenching, but since the reduction of area has been raised its capacity 
for making short bends has been increased. 

When the cold-bending test is specified, after quenching, therefore, it 
would appear from Fig. 412 that this soft material is better able to stand 



Fig. 414. —Effect of Annealing 2 in. X f in. Open-hearth Steel Bars of Different De¬ 
grees of Hardness. (Campbell’s Structural Steel, p. 210.) 

this test than it was in its normal condition. This matter should be proved 
by direct bending tests, however, before being accepted as true. If this 
proves to be true, then quenching greatly improves the steel for all purposes. 

The annealing process seems always to reduce the ultimate strength and 
the elastic limit for all grades of steel, the lowering of the latter, as shown 


* The chemical composition was C = 0.105; Mn = 0.343, P — 0.009; S — 0 024. 



































502 


THE MATERIALS OF CONSTRUCTION. 


in Fig. 414, being about 25 per cent. The elongation is very slightly 
increased and the reduction of area somewhat decreased. By the annealing 
process, therefore, about one fourth of the effective strength of a steel mem¬ 
ber is sacrificed, while its cold*bending capacity is probably reduced. It 
would seem, therefore, that it should be practised only when necessary to 
remove severe internal stresses produced by cold working. 

360. The Billet Test is Characteristic of the Final Rolled Bars and 
Plates.—Mr. Gus C. Henning has shown * that specimen billets rolled or 
forged from the sample of the steel dipped from an open-hearth furnace to 
test its quality give results which are truly characteristic of the products 
rolled from that heat. The tests of these sample billets are commonly called 
“ heat tests,” since one such is made for each heat. If the results of these 
tests agree closely with the tests on specimens cut from the structural forms, 
bars, and plates which are rolled from this material, then these latter may 
be omitted and reliance placed wholly upon the heat tests. The results of 
221 such corresponding sets of tests are given in Table XXV. 

This table also contains results of tests of specimens cut from annealed 
bars and plates. In all the specimen tests on rolled and annealed bars and 
plates an extensometer was used, reading to 0.0001 in. by micrometer-screw 
with electric contact, as shown in Fig. 271. The true elastic limits were there¬ 
fore carefully and accurately determined. This was not done with the heat 
or billet tests, so that no comparison can be made on this score. The yield- 
points were observed by the “ drop of the beam,” which is a quite accurate 
method with this quality of material if the test is not made too rapidly. 

361. The Distribution of the Elongation over an 8-inch specimen 1^ inches 
in diameter is shown in Fig. 415. This shows that the stretch is nearly 
Uniform until the maximum load is reached, after which it begins to neck 
down. From this on to final rupture the stretch is almost wholly confined 
to the necked-down portion. Thus while the elongation near the ends was 
only 21 per cent and the average elongation was about 28 per cent, the 
elongation at the plane of rupture was 75 per cent. 

The Reduction of Area of rectangular specimens is difficult to obtain 
accurately, on account of the resulting curved outlines arising from the 
greater contraction in the middle portions. This action is well shown 
in Fig. 416. If the reduced section is calipered at about one fourth the 
width from each side, the area resulting from taking the product of these two 
dimensions will be insignificant. 

362. The Compressive Strength is the Elastic Limit. —Table XXVI con¬ 
tains the results of some of the most careful experiments ever made on the 
compressive strength of steel bars (see also Fig. 294). These were made by 
Mr. Chas. A. Marshall, C.E.f These results show a practical identity in the 
apparent elastic limit, or yield-point, in tension and compression, and also 


* In Trans. Am. Soc. Mech. Engrs., vol. xm. 
f See foot note p. 341. 





THE STRENGTH OF STEEL, 


503 


TABLE XXV.—COMPARISON OF RESULTS OF TESTS OF SPECIMEN BILLETS 
AND OF SPECIMENS CUT FROM FINAL ROLLED FORMS. 


Tests of Bars. 


Size of 
Bar. 

Kind of 
Test. 

Elastic 

Limit. 

Yield-point 

Tenacity. 

Per cent 
Elonga¬ 
tion in 8" 

Per cent 
Reduc¬ 
tion in 8" 

Modulus of 
Elasticity. 

No. of 
Tests 
Averaged; 


Billet 


47,267 

73.440 

23.6 

39.5 

30,191,000 

3 

7" x 7/8" •< 

Rolled 

35,867 

39,006 

71,540 

25.1 

51.6 

29’799’000 

3 

l 

Annealed 

37,850 

39,083 

69,990 

25.3 

54.2 

31,290,000 

3 

( 

Billet 


45,666 

70,845 

23.3 

41.7 

29,498,000 

4 

7"xlJ" -J 

Rolled 

33,622 

39,334 

71,102 

23.2 

44.7 

30! 837,000 

5 

1 

Annealed 

35,060 

40,140 

67,930 

26.3 

57.0 

31,567^000 

2 

f 

Billet 


44,498 

70,392 

23.3 

41.3 

30,793,000 

3 


Rolled 

29,650 

36.620 

69,750 

24.1 

48.9 

29.939,000 

2 

{ 

Annealed 

33,110 

40,035 

70,860 

25.2 

53.7 

31,410,000 

2 

L 

Billet 


45,010 

71,035 

22.6 

37.1 

29,150.000 

2 

7"x lp' l 

Rolled 

34,725 

38,255 

72.108 

22.8 

40.2 

29,889,000 

4 

1 

Annealed 

38,125 

40,725 

69,800 

24.6 

42.4 

31,444,000 

2 


Billet 


46,103 

69.820 

24.0 

41.8 

29,900.000 

3 


Rolled 

31,550 

36,635 

67,795 

26.0 

»5.0 

30.921.000 

2 

\ 

Annealed 

35,688 

39,860 

68,154 

25.8 

54.8 

31,451,000 

4 

\ 

Billet 


45.508 

70,320 

24.2 

42.5 

30,127,000 

14 

7" xIf" / 

Rolled 

32,890 

37,480 

71,561 

21.6 

38.5 

30,166.000 

19 

I 

Annealed 

35,470 

39,579 

70,450 

23.4 

44.7 

30,934,000 

11 

( 

Billet 


46,319 

71,395 

23 1 

38.3 

29,850,000 

10 

7" x 1 jV ' ■< 

Rolled 

29,606 

34,882 

67,560 

24.2 

46.0 

30,430.000 

12 

! 

Annealed 

34,162 

37,834 

68,070 

24.6 

48.0 

30,510,000 

11 

( 

Billet 


47,350 

71,595 

22.0 

37 9 

29,840.000 

1 

7"xlJ" / 

Rolled 

33,730 

38,000 

70,090 

26.2 

48.8 

30.528 000 

1 

1 

Annealed 

34,620 

38,500 

69,840 

27.5 

57.5 

30,528,000 

1 

( 

Billet 


45,698 

70,665 

23 7 

41.5 

29.500.000 

7 

r'xiu'^ 

Rolled 

32,082 

36,315 

71,269 

23.3 

43.5 

30,759,000 

11 


Annealed 

37,170 

39,152 

69,688 

25.4 

50.1 

31,268.000 

10. 

( 

Billet 


44,950 

68,770 

25.0 

40.0 

28.285,000 

1 

7" x 1 

Rolled 

38,100 

41,040 

74,060 

19.8 

42.0 

31,647,000 

1 

1 

Annealed 

35,000 

37,550 

65,420 

22.9 

35.0 

30,746,000 

1 

( 

Billet 


45,740 

72.330 

23.6 

38.1 

29.455,000 

1 


Rolled 

29,080 

31.510 

66,180 

26.2 

54.9 

32 479.000 

1 

I 

Annealed 

32,100 

36,640 

73,670 

23.7 

50.4 

31,302,000 

1 

i 

Billet 


46,320 

71,630 

20.8 

31.9 

28,535,000 

1 

?' / xlJ" -J 

Rolled 

29,000 

32,750 

71,370 

25.0 

52.9 

28,420,000 

1 

{ 

Annealed 

33,650 

39,060 

71,280 

24.5 

53.7 

31.078 000 

1 

l 

Billet 


45,869 

71.020 

23.3 

39.5 

29,594,000 m x. 

Average •< 

Rolled 

33.327 

36,819 

70,365 

23.9 

4 7.5 

30,484.000 

JLUlctl LNU* 

1 /• 1 

i 

Annealed 

35,167 

39,013 

69,596 

24.9 

46.0 

31,127,000 

1OI 


Tests of Plates. 



t 

Billet 


47,700 

80.966 

20.5 

35 8 

30.60i,000 

5 

1/2" 


Rolled 

47,048 

48.120 

86.572 

19.7 

36.3 

30.061.000 

5 


\ 

Annealed 

39,523 

43,698 

75,155 

24.7 

47.3 

29.901,000 

9 


l 

Billet 


47,737 

82,113 

20.6 

33.9 

29,690,000 

6 

5/8" 

J 

Rolled 

45,895 

48,008 

81,753 

19.9 

40.7 

30,763,000 

6 


\ 

Annealed 

39,792 

42,066 

74,624 

22.1 

47.2 

30,591,000 

9 


( 

Billet 


51,936 

81,818 

21.1 

38.8 

29,612,000 

5 

3/4" 

\ 

Rolled 

44,692 

47,643 

79,127 

21.8 

42.3 

30,879.000 

5 


1 

Annealed 

38,267 

40,067 

72,961 

22.9 

47.8 

31,167,000 

7 


( 

Billet 


50,130 

84,970 

19.7 

30.8 

29,220,000 

1 

13/16" 

1 

Rolled 

45.5S0 

48,280 

88,230 

19.0 

31.2 

29,188,000 

1 


\ 

Annealed 

41,730 

43,590 

77,010 

25.8 

50.8 

30,528,000 

1 


l 

Billet 


49.376 

82.467 

20.5 

34.8 

29,782.000 


Average 

\ 

Rolled 

40,S04 

48,013 

83,920 

20.1 

37.6 

30.223.000 

fin 


1 

Annealed 

39,828 

42,355 

74,938 

23.9 

48.3 

30,722,000 



























































504 


THE MATERIALS OF CONSTRUCTION. 


that the ultimate strength of short bars is the apparent elastic limit. They 
also show the lessened elastic limit and elongation for the larger sizes, all 
being rolled from the same billet, the ultimate strength not varying much. 
Thus for a reduction of ultimate strength from f in. to 2£ i n * diameter of 



Fig. 415. —Showing the Distribution of the Elongation on (62,000-lb.) Steel Specimen 
8 in. long and in. in diameter. (Fr. Com. Rep., vol. in, PI. III.) 


5.4 per cent, we have a reduction in the elastic limit of 20 per cent, and in 
the percentage of elongation of 60 per cent, the ratio of length to diameter 
remaining constant. 

363. The Elastic Limit in Compression marks the beginning of lateral 
flowing of the metal, and the stress under which this action begins depends 





















































































THE STRENGTH OF STEEL. 


505 


TABLE XXVI.—MILD STEEL IX TENSION AND COMPRESSION. 

Comparison of Tensile and Compressive Results with Results of Tests on Short Columns 
of Round and Square Bars from f in. to 2^ in. in diameter, all rolled from one blow 
of Bessemer Steel. Elongations measured on a length equal to ten diameters, by 
means of the Marshall Exteusometer shown in Fig. 271. (From Marshall’s Ex¬ 
periments, Trans. Am. Soc. C. E., vol. xvii, Tables I and II.) 


Size of 
Specimen 

Elastic Limit in Pounds 
per Square Inch 

Ultimate Strength in 
Pounds per Square Inch 

Elongation. 

Reduction 
of Area. 
Percentage. 

in Tension. 

in Compr. 

for -- = 2. 
a 

in Tension. 

in Compr. 

for \ = 12. 
d 

Length of 
Specimen. 

Percentage 

of 

Elongation. 

3/4 

45,181 

45,000 

68,711 

44,970 

8 

26.4 

45.3 

1 

43,880 

45,355 

68,240 

43,540 

10 

25.6 

39.3 

H 

40,903 

42,880 

67,506 

40,455 

12 

26.4 

43.0 

H 

39,795 

42,015 

66,598 

40,150 

15 

25.4 

39.3 

if 

39,105 

41,225 

66,366 

39,700 

18 

24.3 

33.3 

2 

38,207 

39,176 

65,663 

40,300 

20 

23.9 

27.8 

24 

37,655 

36,542 

65,460 

38,030 

22 

13.7 

17.2 

2£ 

36,100 

36,840 


35,650 

25 

10.2 


Means 

40,103 

i 41,129 

66,935 

40,350 


21.9 

35.0 



Fig. 416.—Showing the Manner in which Rectangular Steel Test-specimens reduce in 

Cross-section. ( Engr. News, vol. xxxm. p. 272.) 

on the freedom with which the metal can flow laterally. Thus in Fig. 417 
we have a column compressed over its full cross-section with freedom to flow 
laterally in every direction. This is the usual condition under which the 

elastic limit in compression is found. 

In Fig. 418 the specimen is compressed uniformly over a portion only of 
its surface, and when the elastic limit is exceeded the metal finds escape by 
flowing laterally against the resistance of a ring of unstressed metal. This 
is a condition of restricted flow, and evidently the elastic limit now is much 
higher tfian before. 


































506 


TEE MATERIALS OF CONSTRUCTION. 


In Fig. 419 only the metal towards the centre of the compressed surface 
is constrained to flow under the direct stress, but in attempting to move 
laterally it is held by a ring of metal which is confined and compressed ver¬ 
tically, though inside its elastic limit. To find an escape the metal at the 



Fig. 417. 
Free Flow. 



Fig. 418. 
Restricted Flow. 



Fig. 419. 
Confined Flow. 


centre must force its wav against a much wider ring of metal than in the 
second case, tpid hence the elastic limit now is very much higher than when 
pressed by a flat disk. 

The elastic limit in compression, therefore, is a meaningless expression 
unless the conditions of lateral flow are also stated. 

364. The Author’s Tests of Areas of Contact between Car-wheels and 
Rails.—In Figs. 420 and 421 are shown a series of actual areas of contact 
obtained by pressing sections of a cast-iron car-wheel and of a locomotive 
steel driving-wheel upon the cylindrical top surface of a steel rail. This 
was done in a testing-machine in such a way that there was no rocking 
motion and the area of contact was clearly distinguished.* 

The areas of these surfaces of contact were determined by a planimeter, 
and these are plotted to their corresponding loads in Fig. 422. It will be 
seen that these plot in nearly a straight line through the origin. If such a 
law be assumed, it follows— 

f. That the area of contact increases directly with the load. 

2. That the wean intensity of pressure is a constant for all loads. 

3. That in these experiments this mean intensity of compressive stress, 
for all loads, was about 82,000 lbs. per square inch. 

4. Since the maximum deformation (at the centres of these areas) is 
twice the average deformation (assuming the volumetric deformation to be 
that of a segment of a paraboloid of revolution), then the maximum com¬ 
pressive-stress intensity for all loads is about 164,000 lbs. per square inch. 

5. Since no measurable permanent set was produced by any of these 
loads on either wheels or rail, it follows that the “apparent clastic limits ” of 
the mater inis had not been reached for this condition of contact, although 
the ordinary elastic limit of the rail material, for a free flow as in Fig. 417, 
was about 50,000 lbs. per square inch. 


*See a full account of these tests, showing other areas of contact, in Trans. Am. Soc. 
Civ. Engrs., vol. xxxii. p. 270. 1894. 






























THE STRENGTH OF STEEL. 


507 





Fig. 420. —Steel Driver, 44 in 
diam. Flat tread 




Fig. 421.—Chilled Wheel, 
33 in. diam. New. 


Impressions on 75-lb. Steel Rail. Top Radius, 14 in. Full Size. 















508 


THE MATERIALS OF CONSTRUCTION. 



Fig. 422.—Showing the Relation between the Total Load and the Area of Contact be¬ 
tween Wheels and Rails. (Johnson, in Trails. Am. Soc. C. E., vol. xxxii.) 


^1 















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0 2 4 6 8 10 /2 /4 16 

Fig. 423.—The Elastic-limit Loads per Lineal Inch of Rollers of Various Diameters. 
(Crandall and Marston, in Trans. Am. Soc. Civ. Engrs., vol. xxxii. p. 120 (1894).) 







































































THE STRENGTH OF STEEL. 


509 


These are important conclusions, and should be supplemented and 
supported by further observations of this character. 

In Fig. 423 are shown the results of tests made by Profs. Crandall and 
Marston to find the elastic-limit loads on steel cylinders resting on or 
between steel plates. These results show that the elastic loads vary directly 
with the diameters, these loads per lineal inch of rollers, for mild structural 
steel, being 

p — 880 d, . (If 

where p = elastic-limit load in pounds per lineal inch, and d — diameter of 
roller in inches. 

365. The Moduli of Elasticity in Tension and Compression for various 
sizes and qualities of steel and wrought iron are given in Table XXVII, 

TABLE XXVII. — COMPARISON OF MODULI OF ELASTICITY IN TENSION AND 

COMPRESSION.* 

All results given in one-thousand-pound units, identical material. 


Steel —Tensile Strength less than 100,000 Spring-steel.— Tensile Strength 144,000 
lbs. per Square Inch. Pounds per Square Inch. 


Size 

of 

Bar. 

Tension. 

Compression. 

Size 

of 

Bar. 

Tension. 

Compression. 

Ey 

First 

Loading. 

E ^ 

Second 

Loading. 

Ey 

First 

Loading. 

E, 

Second 

Loading. 

L, 

First 

Loading. 

E 2 

Second 

Loading. 

Ex 

First 

Loading. 

E* 

Second 1 

Loading 

1 rd. 

30,190 

34,420 

29,450 

29,740 

1 rd. 

29,480 

29,760 

28,880 

29,300 

to sq- 

29,850 

29,850 

28,070 

29 010 

1 rd. 

29,390 

29,580 

28,880 

29,200 

1 rd. 

29,280 

29,500 

28,780 

29,420 

TO S Q- 

28,880 

29,420 

29,090 

29,220 

| rd. 

29,830 

29,150 

28,580 

29,420 

to s 4- 

29,200 

29,200 

29,090 

29,350 

Yo ®q* 

29,420 

29,640 

28,380 

28,670 


— 




1 rd. 

29,550 

29,630 

28,680 

28,830 

mean 

29,237 

29,490 

28,985 

29,267 

1 rd. 

29,240 

29 960 

30,070 

30,490 






1 rd. 

29,400 

30,420 

28,980 

29,790 






1 rd. 

30,000 

30,370 

29,260 

29,810 






mean 

29,529 

30,371 

28,884 

29,464 







Wrought Iron. 


Size 

of 

Bar. 

Tension. 

Compression. 

Size 

of 

Bar. 

Tension. 

Compression. 

Ey 

First 

Loading. 

I? 2 

Second 

Loading. 

Ey 

First 

Loading, 

E? 

Second 

Loading. 

Ey 

First 

Loading. 

2? 2 

Second 

Loading. 

Ey 

First 

Loading. 

E% 

Second 

Loading. 

f rd. 

| rd. 

1 rd. 

1 rd. 

1 sq. 

26,800 

26,980 

27,540 

28,990 

27,790 

27,800 

27.500 

27,410 

26,700 

27,540 

29.180 

27,900 

25.840 

25,920 

25,670 

26,020 

27,420 

25,650 

26,490 

26.160 

26,240 

26,440 

26,350 

27,790 

27,300 

1 sq. 

1 rd. 

1 rd. 

1 rd. 

1 rd • 

28,290 

27,590 

28,290 

26,580 

30,190 

28 290 
28.570 
28,480 
28,480 
30,190 

27,100 

27.250 

27,430 

26,500 

29,520 

27,990 

28.570 

28.570 
28,180 
29,910 

1 sq. 

1 sq. 

mean 

27,894 

28,203 

26,734 

27 590 


* From experiments by Charles A. Marshall. M. Am. Soc. C. E., reported in Trans . 


Am. Soc. Civ. Engrs.,v ol. xvii. pp. 62-3. 















































































510 


THE MATERIALS OF CONSTRUCTION. 


these results also being from Marshall’s experiments. They show the rela¬ 
tion between the modulus of elasticity as obtained from the first and from 
the second loading, the first loading not having been carried beyond the 
elastic limit. As the modulus from the second loading is always a little 
larger than that obtained from the first loading, it shows that on the first 
loading there is always a small permanent set, and that moduli of elasticity 
should he observed only after a load has been imposed and removed. The 



Fig. 424.—Showing Variations in the Modulus of Elasticity of Steel Eye-bars, 66,000 
lbs. T. S., after the Elastic Limit has been Passed. ( Wat. Ars. Rep. 1S83.) 

failure to do this may explain some of the low values of this modulus which 
.are often given. 

If the specimen he stretched much beyond its elastic limit, however, the 
mod. of elast. is lowered after each such higher loading, as indicated in 
Fig. 424. 

366. Modulus of Elasticity Independent of the Other Mechanical Prop¬ 
erties.—In Table XXVIII are given the average values of the moduli of 
elasticity from 262 determinations on steels of five degrees of hardness. 
The .mean values for these five classes do not in any case differ from the 
mean of all by more than six tenths of one per cent. As the mean of all is 





























THE STRENGTH OF STEEL. 


511 


TABLE XXVIII.—MODULI OF ELASTICITY OF STEEL ON FIRST LOADINGS, 
WITH VARYING PERCENTAGES OF CARBON, ONE SPECIMEN FROM 
EACH HEAT. * 


Number 
of Heats 
and Tests. 

Average 
Percentage 
of Carbon. 

Moduli of Elasticity E, in Pounds per Square Inch. 

Kind of Steel. 

Lowest Value. 

Highest Value. 

Average Value. 

33 

.09 

28,750,000 

31,540,000 

29,924,000 

Bessemer 

8 

.11 

29,210,000 

30,670,000 

30.020.000 

Open-hearth 

107 

.24 

28,310,000 

31,180,000 

29,996,000 

6 i < < 

89 

.34 

28,140,000 

30,910,000 

29.672,000 

Bessemer 

25 

.72 

28,680,000 

30,860,000 

29,919,000 

Open-hearth 



Weighted 

mean value = 

29,866,000 



* From Marshall’s Experiments, Trans. Am. Soc. C. E., vol. xvn. p. 64. 


TABLE XXIX.—TENSILE TESTS ON ROUND STEEL RODS FROM 1 TO 3 
INCHES IN DIAMETER, ANNEALED AND UNANNEALEI). 

Each recorded result is the mean of three tests. All the results in one horizontal line 


are for tests on material cut from the same three bars.f 


Size. 

Elastic Limit $ in Pounds per 
Square Inch. 

Ultimate Strength in Pounds 
per Square Inch. 

Ratio of Elastic Limit to 
Ultimate Strength. 

Unannealed. 

Annealed. 

Unannealed. 

Annealed. 

Unannealed. 

Annealed. 

Diam. 

Rods 

Rods 

Rods 

Rods 

Rods 

Rods 

Rods 

Rods 

Rods 

in in. 

100 in. 

10 in. 

10 in. 

100 in. 

10 in. 

10 in. 

100 in. 

10 in. 

10 in. 


long 

long. 

long. 

long. 

long. 

long. 

lung. 

long. 

long. 

1 

43,330 

46,970 

45,130 

63,8'iO 

66,050 

62,010 

67.8 

71.1 

72.7 

H 

42,400 

43,300 

42,170 

62,507 

65,020 

62,460 

67.8 

66.5 

67.5 

2 

36,520 

39,570 

36,270 

61,320 

61,420 

58.490 

59.5 

64.4 

62.0 

2± 

34,130 

37,230 

34,300 

58,950 

60,300 

56,790 

57.8 

61.7 

60.3 

S' 

35,700 

36,530 

33,500 

58,550 

59,830 

57,370 

60.9 

61.0 

58.3 



Percentage of Elongation. 

Percentage of Reduction. 

Modulus of 

Size. 













Elasticity of the 


Unannealed. 

Annealed. 

Unannealed. 

Annealed. 

100-inch Bars Un- 








annealed in 








Pounds per 

Diameter 

Rods 100 in. 

Rods 10 in. 

Rods 10 in 

Rods 100 in. 

Rods 10 in. 

Rods 10 in. 

Square Inch, 

in inches. 

long 

long. 

long. 

long. 

long. 

long 

First Loading. 

1 

19.21 

25 6 

22.1 

60.2 

61.1 

65.7 

27,300,000 

H 

21.42 

26.9 

24.9 

55.3 

55.0 

58.4 

21,100,000 

2 

25.62 

30.9 

30.4 

58.8 

59.4 

62.5 

30,000,000 

2| 

23.50 

31.4 

32.5 

56.9 

54.9 

62.7 

30,600,000 

s' 

17.34 

30.6 

33.9 

54.6 

49.8 

61.2 

28,400,000 


f From Kirkaldy's Report, 1891, reports M and HH. 

\ This is the true elastic limit on the first loading ; it was about 5 per cent below the 
yield-point, or the ‘'apparent elastic limit.” 




























































































TABLE XXX.—COMPARISON OF TENSION AND COMPRESSION TESTS ON ANNEALED AND UNANNEALED STEEL BARS 
OF IDENTICAL MATERIAL WHICH HAD BEEN STRESSED BEYOND ITS ELASTIC LIMIT.* 


612 


THE MATERIALS OF CONSTRUCTION 


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THE STRENGTH OF STEEL. 


513 


29,866,000, and this from first loadings, it will not be appreciably in error 
to call the modulus of elasticity of steel 30,000,000. (See also Figs. 398 to 
403, where tensile stress indicated for an elongation of 0.001 is uniformly 
about 30,000 lbs. per square inch, thus giving a modulus of elasticity of 
30,000,000.) . . 

367. The Effect of Annealing on Steel Before and After Overstraining.-_ 

In fable XXIX aie given results of annealing steel bars which have never 
been stressed or worked cold. In Table XXX are given the results of tests 



Fig. 426.—Effect of Length of the Reduced Section on the Strength and Ductility of 
Steel JamesE. Howard (in charge of Tests at the Watertown Arsenal) before Inter. 
Ewg. Cong. 1893. Section of Nav. Eng. and Marine Arch., vol. ii, J. Wiley & Sons, 
New York. 

on overstrained *steel which was afterwards annealed. It will be observed 
that, while it has little effect on soft steel in the normal state, the anneal¬ 
ing largely restores the original qualities to overstrained soft steel, though 
it does not fully do so. The high moduli of elasticity in compression given 
in Table XXX for both the annealed and the unannealed specimens should 
be accepted with caution as being probably erroneous. 












































514 


THE MATERIALS OF CONSTRUCTION , 


368 The Effect of Varying the Length of the Reduced Section,*— “The 
following results of the tests of six specimens from the same 1^-in. steel 
bar illustrate the apparent elevation of elastic limit and the changes in other 
properties due to changes in the lengths of stems which were turned down 
in each specimen to 0.798 in. diameter. (See also Fig. 426.) 


Description of Stem. 

Elastic Limit, 
Pounds per 
Square Inch. 

Tensile Strength, 
Pounds per 
Square Inch. 

Contraction of 
Area, 

Per Cent. 

1.00 ' Iona. 

64.900 

65,320 

68,000 

75,000 

86,000, about 
90,000, about 

94,400 

97,800 

102,420 

116,380 

134,960 

117,000 

49.0 

43.4 

39.6 

31 6 

23.0 

Indeterminate 

.50 .. 

25 *• . 

Semicircular groove, 0 4” radius. 

Semicircular groove, 1/8 1 ' radius. 

V shaped groove. 


“These tests show the progressive elevation of the elastic limit as the 
stems of the specimens were shortened, and the corresponding effect upon 
the tensile strength. The contraction of area, of course, diminishes as the 
other two features increase in value. 

“ The lower tensile strength of the specimen having the V-shaped groove 
was probably due to the excessive concentration of stress at the bottom of 
the groove from inability to elongate or contract, fracturing the metal more 
in detail than happened to the other specimens.” 

In Fig. 427 are shown the results of similar tests made by M. Duguet on 
hard steel and by M. Barba on soft steel bars. In both of these sets of ex¬ 
periments the very short reduced sections have a greatly increased breaking 
strength. 

In this connection it must be remembered that in ductile metals, where 
the reduced section has appreciable length, there is a great reduction of 
area, so that the stress per square inch at rupture on the actual section at 
that time is about twice the tensile strength as computed on the original 
cross-section. In the very short or grooved reduced sections, however, the 
material has no opportunity to reduce in area, and hence the actual ruptur¬ 
ing stress is developed over the full original area. In the case of the sharp 
V-shaped groove the material is likely to tear apart by failing first at the 
outer edges- In other words, the stress is not uniformly distributed over 
the cross section. 

In Fig 428 are plotted the results of tests of the same grade of steel 
(54,000 lbs tensile strength), when tested in the standard form, with par¬ 
allel sides, and when grooved as has long been required for the U. S. Marine 
Service The effect of the groove is to raise the tensile strength from 7000 


51 Quoted paragraphs and table taken from a paper by James E. Howard read before 
the World's Engineering Congress , 1893. 























THE STRENGTH OF STEEL . 


515 


]bs. per square inch on the f inch plate to over 12,000 lbs. per square inch 
on the 1-iuch plate. The grooved specimen, furthermore, gives little or no 


/zqm 


//8m 






88888 






S4000 



Fig. 427. —Showing the Effect of the Form of the Reduced Section on the Tensile 
Strength of Two Kinds of Steel. (Fr. Com. Rep., vol. in, p. 40 ) 


indication of the elastic limit, and no indication of the percentage of elonga¬ 
tion. The requirement of grooved specimens on this service will probably 
soon be abandoned. 

369. Nickel-steel,* being an alloy of mild steel with about 3|- <f 0 of nickel, 
has a very high elastic limit and ultimate strength, combined with great 
ductility, as shown in Fig. 429. This alloy is doubtless destined to play a 


* First made by Marbeau in 1885, and used for armor-plate in 1890. The price of 
nickel steel was 40 to 45 cents a pound in 1894. For a complete study of the influence 
of uickel on pure iron, in all proportions, see Berlin Testing Laboratory Communica¬ 
tions , 1898, vol. iv. p. 222. 




































































































616 


THE MATERIALS OF CONSTRUCTION. 


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Wj 


'0> 


F' 

\d? 

X,< 

y . 

..4 


T///CA 

WSS 

OF A 

’A75 




7s W W W * / 

t 


(Fig. 428.—Showing Relative Results from Grooved and Parallel-sided Specimens 

(Campbell’s Structural Steel, p. 223.) 





Fig 429. —Tension Tests on Nickel-steel. ( Wat . Ars. Rep. 1894, pp. 199 nmi 200 ) 

























































THE STRENGTH OF STEEL. 


51 C>a 


leading part wherever great elastic strength and a reasonable ductility are 
required. It would seem to be especially fitted for bicycle tubing and 
spokes, aerial experimentation, the reciprocating parts of locomotive 
engines, motor carriages, etc., as well as for armor-plates. 

Lhe very remarkable properties of a nickel-steel alloy having high per¬ 
centages of nickel have been investigated by M. Oh.-Ed. Guillaume, and 
his results published in Bulletin de laSociete de VIndustrie for 1898, p. 260. 
These alloys have been studied with varying proportions of nickel up to 50 
per cent, the combined carbon, silicon, and manganese aggregating about 
1 per cent. While the magnetic properties are peculiar and interesting, it 
is only changes of volume with variations of temperature which will be 
referred to here. In this respect these alloys fall into two classes: the irre¬ 
versible, having from 0 to 25 per cent of nickel; and the reversible, having 
25 to 50 per cent of nickel. The former on first cooling from a red heat 
contracts until the temperature 200° F. is reached, when, on further cooling, 
the bar expands continuously to a minimum temperature of — 40° F. If 
reheated, however, between 200° and — 40° it at once expands and contracts 
normally, and does not contract to 200° and then expand, as would be neces¬ 
sary in order to retrace its path. 

The alloys of more than 25 per cent of nickel do not act in this way, and 
hence they are said to be reversible. These alloys have first an increasing 
and then a diminishing coefficient of ex]iansion as the nickel ingredient 
increases, reaching a minimum at 35 per cent nickel, when the coefficient of 
expansion is 0.0000005 per degree F. (0.0000009 per degree C.), or sag one- 
thirteenth that of steel and less than one-twentieth that of brass. (See Fig. 
429 a for ordinary temperatures, and Figs. 429 b and 429c for a range of 
temperatures.) 

This minimum coefficient is so nearly zero that for many purposes it 
may be considered zero, as for steel tapes for surveyors and for measuring 
base-lines, for clock pendulums, etc. For the most accurate geodetic work 
the temperature correction would still be employed and astronomical clock 
pendulums would still be compensated, but the amount of the compensation 
required would be so small that it could be accomplished with very simple 
means. For all such purposes the finished bar or tape should be cooled very 
much below any temperature it would experience in service in order to 
eliminate permanently the peculiar lagging phenomena accompanying the 
first cooling of the material. It is thought these combinations of steel and 
nickel are true alloys and not mere mixtures, as all the accompanying phe¬ 
nomena are very different from any pertaining to the two metals taken sep¬ 
arately. These mixtures are practically, therefore, a new metal, and it may 
have many other peculiarities which are as yet undetermined. These high 
nickel alloys are quite malleable, can be rolled very thin or drawn to very 
fine wires, take a beautiful polish, are almost non-oxidizable, and have great 


5166 


THE MATERIALS OF CONSTRUCTION. 


0.0000120 


0.0000090 


0.0000060 


0.0000030 


ul 

o 





_____ «»- 


_ 


_— 

-L 

<P. PER 

a > 








co 

< 

_i 

UJ 

L- 

-—u_ 

UJ 

Ll. 

O 

if 









o 

Q 

O 

2 

LlI 

O 

o 



V/pE 

RCENT 

\GE OF 

NICKE 

:l 




1,000,000 


0 10 20 30 40 50 60 70 80 90 100 

Fig. 429a.—Coefficients of Expansion, a, and Moduli of Elasticity, E, of the Nickel- 

steels at Ordinary Temperatures. (Guillaume.) 



Fig. 4295.—Coefficients of Expansion per Degree F. of Nickel-steel for Different Per¬ 
centages of Nickel and at Different Temperatures. (Guillaume.) 



Fig. 429c. — Coefficients of Expansion per Degree F. at Different Temperatures and for 

Different Percentages of Nickel. (Guillaume.) 













































THE STRENGTH OF STEEL. 


517 


stiength. They are, therefore, likely to come into very general nse for a 
variety of purposes. From Fig. 429 a it may be seen that the modulus of 
elasticity varies with the coefficient of expansion, though within narrower 
limits. 

370. The Mechanical Properties of Steel as Affected by Forging and 

Rolling. In big. 430 is shown the cross-section of a steel shaft 16 inches in 
diameter (which broke soon after being put in service) from which eight test- 



Fig. 430.—Showing the Varying Character in the Material in Different Parts of the 
Cross-section of a Large Steel Shaft when forged under a Teu ton Hammer. ( Wat. 
Ars. Rep., 1885.) 


specimens were cut, lying symmetrically in a diametral section as shown. 
Four of these were tested as cut from the shaft. The other four were forged 
down after cutting out. The plotted results show— 

1. The elongation of the unforged specimens varied from 21 percent in the. 































































518 


THE MATERIALS OF CONSTRUCTION. 


U_ SO- - A 



_ _ _ fALLQL J8ATL -. 


■specimen taken from near the surface of the shaft to 2 per cent in the specimen 

coming from near the centre. In the forged specimens, 
however, taken from the opposite side of the disk, the 
elongation varied from 28 per cent near the surface of 
the shaft to 24 per cent near the centre, thus showing 
that the material was identical throughout when it had 
been similarly worked. In other words, the material 
near the centre of the shaft was in its primitive con¬ 
dition when first cast, while that near the surface was 
that of well-rolled steel. This shows the necessity of 
forging large shafts under enormously heavy hammers, 
or, better, the necessity of using only hollow-forged 
shafts for such sendee. 

Steel car-axles are now rolled and then finished by 
drawing through a die. In Fig. 431 are shown the 
effects of a series of 16 blows upon a steel car-axle, Sp¬ 
in. in diameter, turned over after each second blow, of 
a drop weighing 1640 pounds and falling from 18.8 to 
28 ft. The deflections from each blow varied from 84 
to 13 in., but the axle remained unbroken after this 
severe treatment. 

371. Steel-welded Tubes.—In Tables VII and VIII, 

pp. 130 and 131, it was shown that steel may be welded 
as securely as wrought iron, but that the temperature 
at which this material welds perfectly lies within com- 


FALL 0F_2_0FI. 



- - - FALL QF2_5_FF — paratively narrow limits. If heated above the upper 
^limit the steel melts and oxidizes, and it is then said to 

have beeh burned. If not heated up to the lower limit 
c= =r - ■ t an imperfect weld is formed. To effect a good weld 

FALL OF28FT in a common blacksmith’s forge therefore requires 

Fig. 431.— Showing the g rea t skill and care. On the other hand, where steel 
Successive Foi ms of p] a j. eg llse d f or tube-making are uniformly heated in 

Car-axle when tested a * lirnace 111 which the temperature can be mam- 
by impact without tained constant and of a given degree, these may then 
Rupture. Wt. of be welded perfectly, especially if this be done by ma- 
drop = 1640 lbs. chinery. The evidence of such perfect welds is fur- 
(Original INIS.) nished in Figs. 432 and 433, where welded steel tubes 
■are shown to have been subjected to the most severe abuse, by cold crushing 
and twisting, and without any failure appearing in any of the welded joints. 

372. Wrought-iron and Steel I Beams and Plate Girders. —When rolled 
into I beams, or when plates and angles are riveted together to form a plate 
girder, the true elastic limit of the beams and girders is below that of the 
•specimen test-pieces cut from the webs and flanges. The ultimate strength 
*of the wrought-iron beams and girders is higher than that of the specimens, 































Fig. 432.—Examples of the Cold Deformation of Welded Steel Tubing, made by the National Tube Works at McKeesport, Pa. 

(From the Iron Aye, Sept. 17, 189G.) 


THE STRENGTH OF STEEL. 


519 














520 


THE MATERIALS OF CONSTRUCTION. 



Iif 
- \ > , 


|Sggl|g 


Fig. 433.—Examples of Welded Steel Tubes twisted Cold", made by the National Tube 

Works. (From The Iron Age, Sept. 17, 1896.) 



Fig. 434- —Bending Tests on Steel and Wrouglit-iron I Beams, 7.6 in. high, on 60-in. 

span. (Tetmajer, vol. in, PI. IV.) 



Fig. 435.— Showing Variation in Moduli of Strength and Stiffness of Steel I Beams with 
Varying Depth. (Tetmajer’s Communications, vol. hi, PI. V.) 
























































































THE STRENGTH OF STEEL. 521 

but with the steel beams and girders the reverse is the case. All these 
relations are shown by the following tables, which are the results of a series 
of very careful tests made by Professor Tetmajer. The moduli of elas¬ 
ticity of the rolled or riveted forms are not appreciably lower than those of 
the materials of which they are composed; but this modulus and also the, 
moduli of strength seem to decrease with increasing heights of beam, as 
shown in Fig. 435. 

TABLE XXXI.-ELASTIC LIMIT AND ULTIMATE STRENGTH OF WROUGHT-IRON 

I BEAMS AS COMPARED WITH RESULTS OF TESTS OF SPECIMENS CUT 
FROM THE WEBS AND FLANGES OF THE SAME. 

(Each result is the mean of two tests. From Prof, von Tetmajer’s Communications, 

vol. IV.) 


Depth 

of 

Beam 

in 

Inches. 

Elastic Limit in Pounds per 
Square Inch. 

Ultimate Strength in Pounds per 
Square Inch. 

Per Cent of 
Elongation. 

Modulus of 
Elasticity of 
I Beams in 
Pounds per 
Square Inch. 

Web 

Speci¬ 

men. 

Flange 

Speci¬ 

men. 

Beam, 

Extreme 

Fibre. 

Web 

Speci¬ 

men. 

Flange 

Specimen. 

Beam, 

Extreme 

Fibre. 

Web 

Speci¬ 

men. 

Flange 

Speci¬ 

men. 

4 

40,520 

42,230 

35,120 

54,740 

57,300 

62,850 

10.4 

19.1 

28,600,000 

6 

38,680 

36,400 

33,270 

51,330 

53,750 

56,450 

7.8 

25.5 

28,300,000 

8 

35,690 

34,840 

33,840 

50.900 

51,900 

53,890 

11.7 

18.5 

28,300,000 

10 

36,120 

34,410 

31,000 

48,490 

51,330 

51,620 

13.1 

15 8 

27,500,000 

12 

31,000 

32,280 

31,570 

44,930 

52,610 

53,180 

9.1 

19.7 

26,500,000 

14 

33,840 

33,700 

27,870 

51,470 

53,460 

53,890 

17.9 

20.5 

27,700,000 

16 

33,130 

31,140 

29,720 

50,480 

50,190 

52,470 

11 9 

22.9 

27,600,000 

Means 

35,572 

35,000 

31,770 

50,334 

52,934 

53,478 

11.7 

20.2 

27,800,000 


TABLE XXXII.-ELASTIC AND ULTIMATE STRENGTH OF WROUGHT-IRON 

PLATE GIRDERS COMPOSED OF A SOLID WEB, FOUR ANGLES, AND TWO 
COVER-PLATES, AS COMPARED WITH THE TENSILE STRENGTH OF THE 
PARTS COMPOSING THEM. 


(Each result is the mean of tests on two beams or on four tension specimens. From 

von T^t major's Communications, vol. iv.) 


Test-specimen. 

Elastic 
Limit in 
Pounds per 
Square 
Inch. 

Ultimate 
Strength 
in Pounds 
per Square 
Inch. 

Percentage 
of Elonga¬ 
tion in 

8 Inches. 

Percentage 

of 

Reduction 
of Area. 

Modulus of 
Elasticity of 
Girders in 
Pounds per 
Square Inch. 

Web-plate lengthwise . 

40,950 

53,320 

14.1 

16.2 


“ crosswise . 


37,400 

51,040 

0.5 

13.9 

0 4 


Cover-plates lengthwise . 

35J 20 

17.0 


Angles lengthwise. 

34,690 

46,350 

8.4 

14.6 


Plate girders 16 in. high. 

25,590 

52,330 

• • • • 

• • • % 

25,990.000 

“ “ 20 in. high. 

“ (t 24 in. lnVh. 

29,860 

52,040 

50,620 

47,210 

.... 

I • I ' 

25,250,000 

26,430.000 

“ “ 28 in. high . 

27,580 

* 

• • • • 

26,220,000 

Mp«in of the nnrts . 

38,720 

27,680 

47,050 

50,550 

9.2 

11.8 


Mean of the girders . 

• • • » 

• • • * 

25,970,000 

--u 
















































































522 


THE MATERIALS OF CONSTRUCTION. 


TABLE XXXIII. — ELASTIC AND ULTIMATE STRENGTH OF MILD-STEEL PLATE 
GIRDERS COMPOSED OF A SOLID WEB, FOUR ANGLES, AND TWO COVER- 
PLATES, AS COMPARED WITH THE TENSILE STRENGTH OF THE PARTS 
COMPOSING THEM. 


(Each result is the mean of tests on two beams or on four tension specimens. From 

von Tetmajer’s Communications , vol. iv.) 


Test-specimen. 

Elastic 
Limit in 
Pounds per 
Square 
Inch. 

Web-plate lengthwise. 

52,830 

53,040 

51,190 

39,960 

“ crosswise. 

Cover-plates lengthwise. 

Angles lengthwise. 


Plate girders 16 in. high. 

32,560 

35,690 

33,700 

32,280 

“ 20 in. high. 

“ “ 24 jn. high. 

“ “ 28 in. high. 


Mean of the parts. 

Mean of the girders. 

49,130 

33,550 



Ultimate 
Strength 
in Pounds 
per Square 
Inch. 

Percentage 

of 

Elongation 
in 8 Inches. 

Percentage 

of 

Reduction 
of Area. 

Modulus of 
Elasticity of 
Girders in 
Pounds per 
Square Inch. 

64,560 

24.1 

59.5 


65,980 

20.0 

46.2 


64,840 

25.0 

56 2 


53,750 

31.0 

66.1 


55 310 

• % 0 


27,700,000 

54,320 

• • • • 

• • • • 

28,310,000 

55,030 

• • • • 

• • • • 

28,510,000 

53,750 

• • • • 

• • • • 

28,140,000 

62,280 

25.0 

57.0 


54,600 

.... 

• • • # 

28,165,000 


373. The Effect on Mild Steel of Stressing it Beyond its Elastic Limit. 

~—Both wrought iron and rolled steel, in their normal state, have “ apparent 
elastic limits” in tension and in compression numerically about equal. If 
this material be stressed much beyond these limits, however, in either direc¬ 
tion, its elastic limit in this direction is numerically raised to about the limit 
of its greatest stress, while the elastic limit in the opposite direction is 
greatly lowered or even reduced to zero. This is well shown in Figs. 436 
and 437. Thus in Fig. 436 a steel specimen was stressed several times in 
tension between zero and 45,000 lbs. per square inch, when it was put in 
compression to 50,000 lbs. per square inch, at which load it passed its elastic 
limit and began to flow. After compressing it 0.007 of its length the load 
was removed and simultaneous readings of load and deformation taken 
while the load was coming off, as shown in the figure. The specimen was 
then worked between 10,000 lbs. tensile and a like compressive stress, then 
between zero and 20,000 lbs. tension, and zero and 40,000 lbs. tension, and 
finally between zero and 50,000 lbs. per square inch tension, when it bad 
lengthened 0.004 beyond its original length as' shown in Fig. 436. It was 
then put in compression under a load of 50,000 lbs. per square inch, which 
compressed it 0.004 belcuv its original length, while a subsequent tensile 
stress of 50,000 lbs. brought it nearly back to its previous deformed length 
under this tensile stress. The diagram shows the following remarkable facts: 

1. A permanent deformation of one half of one per cent in either tension 
or compression entirely destroys the perfect elasticity of the material under 
the opposite hind of stress. 















































THE STRENGTH OF STEEL. 


523 


This is shown by the fact that the stress-diagram becomes a curved line 
under all stresses of one kind after having been given a small permanent set 
in the opposite direction. Hence we have: 

2. The elastic field which is symmetrically placed about the line of zero 



stress in the normal specimen becomes wholly limited to that side of this axis 
on which the stress has exceeded the elastic limit. 

A similar set of experiments, plotted in Fig. 437, was followed by the 
annealing of the bar, after which it showed again its normal elastic limits in 




















































524 


TEE MATERIALS OF CONSTRUCTION. 


both tension and compression, which were in turn again destroyed by 
deforming the annealed bar 0.003 beyond its elastic limits, as before. 
Hence we may say: 

3. Annealing an overstressetl bar restores it fully to its normal condition 
of perfect elasticity in both tension and compression. 

Both of these diagrams are very instructive and will bear close study. 
Many more such could be plotted from the tabulated results found in the 



FiG. 4o 7.—Alternate Tensile and Compressive Distortions of a Steel Bar before and after 

Annealing. {Wat. Ars. Rep. 1889.) 


Reports of the Watertown Arsenal, from which the data for these were 
obtained. 

The effect on the ultimate strength of 60,000-lb. steel of pulling it 
nearly to final rupture is shown in Fig. 437 a. This also gives some idea of 
the homogeneity of the steel. Here, after the specimen had necked down 
under the tensile load, but before it broke, it was removed, a continuous 
screw-thread cut on it, and a series of grooves were cut in it as shown. The 
bar was then broken in tension at all these grooves in succession, with the 
results as shown in Fig. 437«. The original tensile strength was about 
57,000 lbs. per square inch, the final breaking stress on the grooved sections 
was about 100,000 lbs. per square inch, while the final stress on the groove 
placed at the centre of the necked-down portion was 155,000 lbs. per square 
inch. A portion of this increase in strength is due to the normal difference 
between the strength of a grooved and of a parallel-sided specimen, as 
shown in Fig. 427. After allowing for this difference there still remains a 
great increase of strength due to the previous drawing out and the interven¬ 
ing rest the specimen had experienced. 










































THE STRENGTH OF STEEL. 


525 


The results of similar tests on unstressed or normal bars are shown in the 
original plate from which Fig. 437 a was taken, which go to show that grooved 
sections on the same steel bar may develop breaking tensile stresses which 
differ from each other by as much as 20 to 25 per cent. No such differences 



SPPORf TfST/M 



I W W 

i . . i , . - .4 . u' 1 I 

(*— S3 - — +/S 1* t/jf 


M 


Afflf-y&fBBSS' -&/V ORpOBVAp - ■NPfO//PffA*;= ' , l 4R:S PER SO-mm. 

• • !!!■!•; =j *6,900 ISS.PtfSQ./N. 


**) Ad. 

\/~7/:8 RES SO. mm. 
7S.3 



=/R2m/SS. PESSQ./M 


1 ^/SSSR RIBS BEB SO. /M 
Fig. 437a. (Rep. Fr. Com.) 


would be observed on specimens with parallel sides cut from the same bar, 
and hence we must conclude that results of tests on grooved sections of steel 
are very erratic and unreliable. 

374. Shearing Resistance of Steel.—Prof. A. B. W. Kennedy, by means 
of the apparatus shown in Fig. 311, obtained values of tensile and shearing 
resistances of various steels given in Table XXXIV. 


TABLE XXXIV.—SHEARING RESISTANCE OF STEEL.* 


Kind of Steel. 

Number 
of Tests 
Averaged. 

Tensio 

Elastic Limit, 
Pounds per 
Square Inch. 

n Test. 

Ult. Strength, 
Pounds per 
Square Inch. 

Shearing 
Strength, 
Pounds per 
Square Inch. 

Ratio of 
Shearing to 
Tensile 
Strength. 

Landore Siemens steel.. . 

2 

37,500 

57,000 

47,500 

0 829 

4 1 ‘ < » 4 

2 

40,000 

63,500 

51,000 

0 800 

<< a a 

3 

37,000 

64,000 

52,000 

0 811 

a a n 

6 

40,600 

69,000 

56,000 

0.807 

Weardale Bessemer “ ... 

6 

44,000 

71,000 

51,000 

0.715 

Bessemer steel. 

4 

51,500 

78,000 

64.000 

0.823 

44 ii 

4 

62,000 

82,000 

59,000 

0.721 

Crucible “ . 

2 

69,500 

116,000 

74,000 

0.632 

Bessemer “ . 

2 

70.000 

118,000 

79,000 

0.670 


* From Proc. Inst. Meek. Engrs. 1885, p. 262. 


From the above table, which is simply corroborative of a vast amount of 
similar data, we may reasonably use 0.8 as the ratio of shearing to tensile 
strength of mild or structural steel. 










































































































526 


THE MATERIALS OF CONSTRUCTION. 


375, The Frictional Resistance of Riveted Joints.* —The contraction of 
rivets in cooling is always much more than their elastic stretch. Thus if the 
modulus of elasticity be taken at 30,000,000, and the elastic limit of rivet- 
steel at 30,000 lbs. per square inch, then the elastic stretch is 0.001 of the 
length. But as the contraction per degree F. is 0.0000065, it follows that 

/_2^5-\ = 154° F. change of temperature would bring rivets to their 

\0.0000065/ 

elastic limit if they were not allowed to contract. Evidently, therefore, all 
well-driven rivets in plates which are tightly clamped together when the rivet 



24,000 


20,000 


/ 2,000 


8,000 


4000 





! 

J 


s - 




l 


8 


1 

1 














K 















<T 













4 



































y l 














2 

TOL 

~TC 

’// 

W, 

Wl 

■> 

> 


0 . 02 , 0.04 0.06 


Fig. 438. Fig. 439. 

Fig. 438. —Showing the Successive Stages of the Slipping of Riveted Plates. 

(M. Dupuy in An. d. Fonts et Chavssees, 1895.) 

Fig. 439. —Autographic Stress diagram of a Double-strap Butt-riveted Joint with one 
rivet on each side of joint, showing slips at aa! and bb'. (An. d. Fonts et Chaussees, 
vol. IX, 1895.) 


is driven, and so held till the rivet cools, are left in a state of tension exceed¬ 
ing their elastic limits. If the coefficient of starting friction be taken at 
0.4, and the elastic limit of steel rivets be taken at 30,000 lbs. per square 
inch, and of iron rivets at 25,000 lbs. per square inch, it follows that the 
frictional resistance would be 12,000 lbs. per square inch of rivet section for 

* Riveted joints are a kind of structure the strength and design of which do not fall 
within the scope of this work. The elements of the strength of such structures, however, 
are properly treated here. 


























































































THE STRENGTH OF STEEL. 


527 


steel rivets, and 10,000 lbs. per square inch of rivet section for iron rivets, 
in lap-joints, and twice these amounts for butt-joints with two cover-plates, 
since in that case there are two frictional surfaces on each of which the full 
tensile stress in the rivets acts. Theoretically, therefore, we might expect a 
frictional resistance of 12,000 or 24,000 lbs. per square inch of rivet-surface 
for lap and butt joints respectively when the rivets are of steel, and of 
<10,000 or 20,000 lbs. when the rivets are of iron. 

Since the plates are clamped together much more firmly when-steam or 
hydraulic riveting-machines are used than when the rivets are driven by 
hand, so the experiments show a much higher frictional resistance for 
machine-driven rivets. To secure the greatest frictional efficiency the 
machine pressure should remain on until the rivet has cooled, but in ordinary 
commercial work this is seldom done. 

M. Dupuy has carefully and fully investigated this question.* He shows 
that after cooling the rivet does not fully fill the hole, as shown in Fig. 
438 (1). The first slip, therefore, when a butt-joint has one rivet on each 
side as shown in Fig. 438 (2), is that which brings the centre plate against 
the rivet. This is shown at a and a ' in Fig. 439, this being a reduced auto¬ 
graphic stress-diagram for the joint shown in Fig. 438. The slip at a 
occurred under a load of 17,500 lbs. per square inch of rivet area wdien the 
centre plate came up against the rivet on one side of the joint, and the slip 
at a' marks a similar movement on the other side at 18,500 lbs. per square inch 
of rivet area. After these movements had occurred the load was increased to 
28,000 lbs. per square inch of rivet area, when the rivet-heads slipped on the 
cover-plates, as shown in Fig. 438 (3), and on the stress-diagram in Fig. 439 
at b. Soon after the same action occurred at the other rivet, marking the 
deformation at b ' in Fig. 439. All these four slips were sudden, and were 
accompanied by a sharp report like a pistol-shot. After the spaces had all 
closed up in this way the deformation was gradual, and the rivet would 
then be acting as a bolt, and be subjected to a shearing stress and deforma¬ 
tion as shown in Fig. 438 (4). 

376. The Stresses per Square Inch of Rivet Section at which the First 
Slipping Occurs, as determined by M. Dupuy, with an extensometer 
(called by him an elasticimeter), are given in Fig. 440. They are presented 
in this form in order that the relative frictional efficiencies of different 
methods of riveting may be read at a glance. These results were obtained 
by cutting the plate along the centre line of the rivets and then pulling out 
the two halves of these rivets as indicated in the figure. In this way the 
frictional resistance of the rivet-heads was correctly obtained without any 
complication with bearing or shearing resistance, as must always be the case 
when pulling actual riveted joints. 

From tests on riveted joints made at the Watertown Arsenal (1882) we 
find the following values of frictional resistance on plates with elongated 
holes, hand-riveting: 


* In An. d. Ponts et Chaussees, 7th series, vol. ix, 1895 





528 


THE MATERIALS OF CONSTRUCTION. 


Frictional Resistance 
on one Surface in 
Pounds per Square 
Inch of Rivet Area. 


Steel plates, f-iu. iron rivets, lf-in. grip, lap-joint, 4 tests. 14,550 

Iron “ f-in. “ “ 1-in. “ “ “ 4 “ . 14,100 

“ “ f-in, “ “ 1-in. “ butt-joint, 2 cover-plates, 2 tests 9,000 


It thus appears that the frictional resistance is not twice as much on a 
butt-joint having two cover-plates as it is on a lap-joint. The reason may 

/&000 


/QOOO. 



//roc. press. -awry, mvet white //or 


RELIEVED 


CON I'D. 


OLD 


5,000 


& 


RIVETING 


WHITE 




k 


'O N^L/EEG. POTSS. ~r/vet polo 


1 

I 

0 




Tr-*- : 






i- 

__ _i 


Fig. 440.— The Slipping Resistance of Steel Rivets in Pounds per Square Inch of Rivet 
Cross-section for Various Conditions of Driving. Each result is the average of 25 
tests on single rivets from £ inch to 1.2 inches diameter. Plates and rivets cut on 
the diametral lines and each half of rivet pulled out as shown. (M. Dupuy in An. 
d. Fonts et Chaussees, 1895, p. 105 ) 



Fig. 441.— Stress-diagram of Test of Double-butt-strap Riveted Joint, Steel plates 0.662 
in. thick and 20 in. wide. Thirteen f-in. steel rivets, machine-driven, on each side 
of joint. Drilled holes §§ in. diameter. ( Wat. Ars. Rep. 1887, p. 892.) 

be that the distortion of the lap-joint increases the frictional resistance by 
putting an additional tensile stress on the rivet from the bending of the 
plates. 



















































THE STRENGTH OF STEEL. 


529 


Since the frictional resistance is thus seen to depend directly upon the 
total shearing area of the rivets, whether these be in single or in double 
shear (although in double shear the frictional resistance on each bearing 
surface seems to be less than in single shear), there would seem to be no 
advantage in designing riveted joints for frictional resistance. It seems 



Fig. 442.—Stress-diagram of a Test of a Double-butt-strap Riveted Joint. Steel plates 
| in. thick and 16.5 in. wide. Eleven 1-in. steel rivets, machine-driven, in three 
rows on each side of joint. Straps f in. thick. Drilled holes 1 T \ T in. diameter. 
(Wat. Ars. Rep. 1887, p. 901.) 


probable, however, that all riveted joints in practice do their work through 
friction alone, and that in no case are the rivets subjected to either shearing 
or bearing stress. But when the joint is dimensioned for shear, it is likely 
to be also properly designed for frictional resistance. In the case of double 
shear, riveted joints are usually proportioned for bearing stress, and here it 



Fig. 443.—Showing Manner of Failure of a Triple-riveted Steel Plate. Figures indicate 
thickuess of plate at that place. (Wat. Ars. Rep. 1887.) 

would seem to be proper to make due allowance for the frictionax resistance 
which, for all working loads, will at least greatly reduce the bearing stress. 

The frictional resistance of joints containing double or triple rows of 
rivets cannot be observed, because all the rivets do not draw with the same 
tensile force, and hence the slipping is progressive and without any sudden 
manifestation. This is well shown by Figs. 441 and 442, which are charac¬ 
teristic of a great many such tests made at the Watertown Arsenal. Evi- 




















530 


THE MATERIALS OF CONSTRUCTION. 


dently it would be impossible here to locate the point of initial slipping. 
This explains Prof. Kennedy’s discrepant results on this class of joints, as 
recorded in the Proceedings of the Institution of Mechanical Engineers 
(London) for the years 1885 and 1888. He here records the loads for 
which “ visible slip began”; but as he used only a hand magnifying-glass, 
and the movement was a gradually progressive one, it would be quite 
impossible to obtain consistent or rational results. In fact, for such joints 
no such stage of the test exists, since the slipping does not occur over the 
entire joint at any one time. 

377. The Bearing Resistance of Steel and Iron Plates is shown in Fig. 
444. This is seen to increase directly with the distance of the hole from 



Fig. 444.—Bearing Resistance on Rivet-lioles at Rupture by Tearing Out of Hole. The 
steel plates were of 60,000 lbs. tensile strength. ( Wat. Ars. Rep. 1882.) 

the edge of the plate. When this distance agrees with ordinary practice 
the resistance is so high that it would seem a working bearing stress of 

















































THE STRENGTH OF STEEL. 


531 


16,000 lbs. per square inch might be employed for iron, and of 24,000 lbs. 
per square inch for steel, plates. The stresses here plotted were the bearing 
stresses at rupture, where the plates had so reduced in thickness as to 



Fig. 445.—Variation in Strength of 1-in. Plate for Varying Widths at Bottom of Groove. 
Each plotted result is the mean of from three to eight tests. ( Wat. Ars. Rep. 1882.) 



Fig. 446. _Elfects of Punching, Reaming, and Shearing. No. 5 has punched holes and 

sheared edges. No. 6 has punched and reamed holes and planed edges. (Engr. 

News, vol. xxxiii. p 291.) 
































































532 


THE MATERIALS OF CONSTRUCTION. 


destroy all frictional resistance. Much more, then, could high working 
stresses be employed, since for these the frictional resistance is very great. 
The author believes that the ordinary rules for proportioning riveted joints 
might well be modified so as to allow higher bearing stresses, especially on 
steel. With wrought iron, especially when the stress is transverse to the 



Fig. 447.—Effects of Shearing and Punching on Bessemer-steel Plate i in. thick. 
Specimen 7 had sheared edges and punched holes. Specimen 8 had planed edges 
and drilled holes. ( Engr. News , vol. xxxrir. p. 291.) 




f. 2, 3. 

Fig. 448. —Showing that Injury in Case of Shearing and Punching comes from the 
Compression of the Metal Necessary to Produce the Shear. Nos. 1 and 2 were bent 
cold, with the compression edge on convex side ; No. 3 was bent with compression 
edge on concave side. {Engr. News, vol. xxxiii. p. 290.) 

fibre, more care must be exercised, as this material is liable to be very weak 
in this direction. 

378. The Tensile Strength of Grooved Plates is a measure of the tensile 
strength of a riveted joint when failure occurs by tearing the plate. This 
strength is found to be a function of the width of the net section at the 


























THE STRENGTH OF STEEL. 


533 


bottom of the groove, as well as of the method of obtaining the hole, and of 
the character of the material. These effects are all shown in Fig. 445 for 
J-in. plates of wrought iron and of 56,000-lb. steel. The steel, being more 
ductile, is stronger in the grooved than in the plain (standard) section, 
while the reverse is the case with wrought iron, except with drilled speci¬ 
mens, where the width of the net section was less than If in. 

379. The Injurious Effect of Punching and Shearing is Found on the 
Compressed Side Only.—In punching and shearing cold metal it seems to 
be the compression produced by the shears or by the die-plate which injures 
the metal here and makes it brittle by cold flowing. This is clearly shown 
in Figs. 446 and 448. Thus in Fig. 446 (5), when the punched plate is 
bent with the punch (or upper) side in tension, no cracks appear about the 
punched holes, but when the die (or lower) side of the hole is on the 
tension side of the bent plate, Fig. 446 (5), many cracks appear and radiate 
from such openings. When these holes are reamed, however, as in Fig. 446 
(6), no such cracks develop. 

Similarly, in Fig. 448, when a bar is cut off with two sheared edges, and 
if both pressed corners (from having turned the plate over) are on the same 
side of the bar, and this side be put in tension, as in Fig. 448 (1), then it 
breaks as shown. If these pressed edges are on opposite sides of the bar, it 
breaks only at that edge, as in (2), while if both sheared edges have been 
planed, as in (3), it bends without cracking. 

380. The Avoidance of Scarfed Joints. —This may be effected as shown 
in Fig. 449. Here lap-joints are used in one direction and butt-joints in 



Section A- B. 

Fig. 449.— Proper Method of Joining Riveted Work in Stand-pipes and Boilers when 
single butt-straps are used. ( Engr. News, vol. xxxiii. p. 290.) 


the other, with one cover-plate. This requires twice as many rivets in this 
direction, but it makes a much neater and stronger construction and it avoids 
the heating of one corner of every plate for the purpose of scarfing it down 
to a thin edge, as must be done where three plates come together in a 



















































534 


THE MATERIALS OF CONSTRUCTION. 


lap-joint. In the figure all the outer edges are planed to a bevel for 
calking.* 

381. Steel Specifications. —For three sets of specifications, by a Com¬ 
mittee of the American Society of Civil Engineers, by the Association of 
American Steel Manufacturers, and by Mr. H. H. Campbell, Supt. Steel 
Works at Steelton, Pa., see Appendix D. 

382. The Influence of the Form of the Thread on the Strength of 
Screw-bolts. —This subject lias been investigated by Prof. Martens,! and his 
results are here given. 

Two grades of mild steel were used for these bolts, all of which were cut 
from round bars originally 35 mm. (1.4 in.) in diameter. The softer 
material, having a tensile strength of 53,500 lbs. per square inch, was used 
for screw-bolts approximately one inch in diameter, and the harder material, 
having a tensile strength of 02,000 lbs. per square inch, was used for the 
screw-bolts, which were reduced to approximately one-half inch in diameter. 
Four such bolts were made of each of these sizes for each of the four styles 
of thread shown in Fig. 450, making in all 32 bolts with screw-threads 



B D 

m/Tiwm mums 




Fig. 450. 



which were tested. Two of each of these sets were tested in plain tension, 
the pulling force being applied to the inner face of the nut at one end, and 
increased until rupture occurred. The other two bolts of each set were 
tested also in tension, but under a torsional action resulting from the con¬ 
tinuous turning of the nut as the load increased to rupture. In this case 
the distortion resulting from the permanent elongation of the bolt was 
nearly all taken up by the movements of the testing-machine, the distortion 
taken up by the turning of the nut being the least possible to maintain a 
continuous torsional action at this point. 

The same bars were also tested as plain tension-test specimens with cylin¬ 
drical bodies, and again with grooves turned into them of the same shape as 

* See The Locomotive for Nov. 1896 for a full discussion of quadruple riveted, double¬ 
butt-strap joints having an efficiency of 95 per cent. 

f At the request of the German Society of Civil Engineers. The results were pub¬ 
lished in Zeits. d. Ver. Deutsch. Ing. for April 27, 1896. The abstract here given was 
made by the author and published in the Digest of Physical Tests for July 1896. 






* G. = grooved ; T. = threaded 


THE STRENGTH OF STEEL. 



535 


TABLE XXXV.—ABSOLUTE AND RELATIVE STRENGTH OF THREADED BOLTS IN POUNDS PER SQUARE INCH. (MARTENS.) 







































































536 


THE MATERIALS OF CONSTRUCTION 


the corresponding screw-threads, leaving the same diameter at the bottom 
of the groove as obtained at the base of the threads. The actual and com¬ 
parative average results of all of these tests are given in the following table, 
from which the following conclusions may be drawn: 

1. When subjected to plain tension both the screw-threads and the 
grooved sections were stronger than the plain bars of the same net area of 
cross-section, this excess of strength having an average value of about 14 per 
cent. This excess of strength is due to the re-enforcing action of the 
shoulder in the case of the groove, and of the threads themselves in the case 
of the screw. 

2. There is no very marked difference in the average strength of the 
bolts on which the several styles of thread were cut, the perfectly sharp 
groove shown at A being slightly stronger than the others. 

3. The weakening effect of the tinning of the nut under stress at rup¬ 
ture is much less than might have been predicted, when the distortion of 
the screw below the nut by permanent elongation is taken into considera¬ 
tion. The tests indicate for this case a strength of the one-inch bolts about 
20 per cent less than that of the plain bars, and of the one-half-inch bolts 
about 15 per cent less than that of the plain bars. 

4. In general it may be said that the turning of the nut upon the bolt at 
rupture reduces the strength of the net section of the bolt by about 30 per 
cent. 

5. It is very probable that the four forms of screw-threads here shown 
would show very different results under fatigue tests from repeated stresses, 
and also for static loads on high-carbon steel. Under repeated loads and 
under shock it is probable that the sharp re-entrant angle shown in Fig. 450 A 
would develop incipient cracks much earlier than either of the other forms, 
and that probably the Whitworth thread, shown in B , would be the last 
to develop this kind of weakness, either with soft metal under repeated loads 
or with high-carbon steel under static loads. No such tests have as yet been 
made. It is to be hoped that this subject will soon be investigated, as it is 
of far more importance than the mere matter of static strength. 


I 


i 

CHAPTER XXVII. 

THE FATIGUE OF METALS. 

383. Fatigue Defined. —It has been found from experiment that metals 
will fail under loads much less than their ultimate strength when such loads 
are repeated or reversed many thousands or perhaps millions of times. It 
has been commonly supposed that these repetitions or reversals caused a 
general deterioration of the metal so stressed, so far as its cohesion is con¬ 
cerned, which deterioration has been known by the term fatigue. It is now 
known, however, that no such general deterioration takes place, but that 
some of the millions of incipient defects or “micro-flaws” in the spec¬ 
imen gradually extend their weakening influence, in an irregular plane of 
cross-section, which ultimately becomes the plane of rupture, while the metal 
immediately adjacent to this plane remains perhaps wholly uninjured. In 
fact no tests of metal, on specimens as closely adjacent to such planes of 
rupture as it is possible to procure them, have ever shown any deteriorating 
effects of the repetitions or reversals of stress to which this metal had been 
subjected. The word “ fatigue,” therefore, is scarcely the proper term to 
apply to this class of failures. The gradual fracture of metals would be a 
more truly descriptive term to use. 

384. The Micro-flaws in Steel have been studied exhaustively by Mr. 
Thos. Andrews, F.R.S., M. Inst. C.E. of Sheffield, England, and described 
in Engineering of July 10, 17, and 24, 1890. Some of his illustrations are 
here reproduced in Eig. 451. The large flaws in Nos. 3, 4, 5, and 6 are 
due to small blowholes, while the dark intercellular spaces in Nos. 1 and 2 
are largely composed of the sulphide of iron, which, so far as it destroys the 
continuity of the crystals, makes the iron weak and brittle. These and 
similar incipient faults, of which there are probably scores in every square 
inch of any iron or steel cross-section, are doubtless the initial cause of the 
weakness developed by repeated loadings. These breaks in the continuity 
of the metal cause the stress to be concentrated at their edges, and the con¬ 
stant variation of this stress, near or at the elastic limit, with its accompany¬ 
ing molecular movements, gradually extends the fracture. Evidently there 
can be no regularity of action of such causes, and hence no very rigid rule or 
law for such failures. Even two specimens cut from the same bar may act 
very differently, to say nothing of specimens made by the same processes at 


538 


THE MATERIALS OF CONSTRUCTION. 



1. Micro-flaws x 250 ; Sulphur 
= 0.25 per cent. 


2. Micro-flaws X 200 ; Sulphur 
= 2.00 per cent. 


C 



3. Micro-flaws X 250. Siemens- 
Steel Boiler-plate. 


4. Micro-flaws x 250. Siemens- 
steel Propeller-shaft 




5. Micro-flaws X 400. Bessemer- 
steel Railway-axle. 


6. Micro-flaws x 250. Bessemer- 
steel Rail. 


Fig. 451. —Views of Internal Micro-flaws in Steel. (Andrews in Engineering, July 10, 

1896.) 














THE FATIGUE OF METALS. 


cm 


different times and at different works, or of specimens made by different 
processes and having different chemical compositions. Evidently the results 
of fatigue tests would be extremely various, and this is the experience of all 
the experimenters in this field of investigation. 

385. Wohler s Tests. —The first systematic study of the fatigue of metals 
was made by M older from 1849 to 1870 for the German government, and 



these were continued after his death by Spangenberg. As Wohler’s tests 
have become historically famous, his appliances are here described. 

For Repeated, Tensile Stresses Wohler used the apparatus shown in Fig. 
-±52. Here the specimen A is stressed through the lever L and spring s 



Fig. 453. —Wohler’s Machine for Repetition of Bending Stress. 

acting on the auxiliary lever m. The pull of the spring s is measured by 
the starting of the adjusted calibrated spring s' through the terminal lever g. 
The nut at the rod d is adjusted to give the minimum load on the spring s 
by starting the spring s' when adjusted to a particular tension, and the cam- 
movement of d to its extreme downward position is made to give the requi¬ 
site maximum stress in the specimen by adjusting the spring s' so as just 






































































































































540 


TEE MATERIALS OF CONSTRUCTION. 


to lift at this position of d. The rod is adjustable by means of a turn- 
buckle. In this way the bar A can be stressed in tension between any chosen 
limits. 

For Rej)eated Bending Stresses Wohler employed the machine shown in 
Fig. 453. Here the specimen A is bent downwards by the adjustable rod q 
attached to the rocking lever below. If the load is not to be wholly removed 
each time, a residual deflection is maintained by means of the abutting screw 
in the lever m. Both the maximum and the minimum loads are fixed by 
means of the calibrated spring s acting on the attached lever g. 

For Reversals of Bending Stress Wohler made use of the apparatus 
shown in Fig. 454. Here two test-bars A A are attached by a driving fit to 



Fig. 454. —Wohler’s Machine for Reversals of Bending Stress. 


the central axle, which is rotated by a belt and pulley. The ends of the 
test-bars are held down by the calibrated springs ss , so that the bending 
stresses are reversed at every revolution. Of course the test-specimens are 
trued up to run truly after driving and before loading. 

For Repetitions of Torsional Stress Wohler devised the machine shown 
in Fig. 455. Here the specimen A is fastened to the moving lever L at one 



Fig. 455. —Wohler’s Machine for Repetition of Torsional Stress. 


end and to the resisting levers hh at the other. The lever L is actuated by 
the connecting-rod l and the lever 0, which in turn is moved by the recip- 








































































































































THE FATIGUE OF METALS. 


541 


rocating-bar C. If tlie bar is stressed in opposite directions, then botli the 
levers g and g' are in use, and the calibrated springs ss act to limit the tor¬ 
sional moment to the required amount as before. 

386. The Results of Fatigue Tests. —The most careful and complete set 
of fatigue tests under repeated stresses was made by Bauschinger. His 
results on mild-steel plates are shown in Fig. 456. For this material, which 
had.an ultimate strength of 64,000 lbs. per square inch the repetition limit 
was found to be about 35,000 lbs. per square inch, or about the elastic limit 


70000 








sqm 

kMIT/M/JT. 

r STfff/VC 

7 // 





*v 

!\ 







sqooo 

s \ 

^ \s 







ty 







sqm 

F* 

' 






| 






4 







—-- 

sqm 

6 

^ /VA 

'ms/rs 

Of fffO 

T/T/O/V, 

1 //V M/* 

U/3/7S 


i / 

3 3 4 3 S 7 


Fig. 456.—Bauschinger’s Fatigue Tests ou Mild-steel Plates under Tensile Stress Re¬ 
peated from Zero. Attached figures indicate number of tests averaged. 

of the material. This material was very uniform in quality and gave quite 
consistent results. In general the results of such tests are very discrepant, 
as should be anticipated from the nature of the causes operating to produce 
the final fracture. 

In Fig. 457 are given the results of a series of tests by reversed bending 
stress on various grades of steel and on cold-rolled wrought-iron bars. As 
the steel bars seemed to give way under about the same stresses, irrespective 
of their several elastic limits and ultimate strengths, they have here all been 
averaged to bring them into comparison with the tests on the wrought-iron 
bars. These results seem to be favorable to wrought iron rather than to this 
particular kind of steel. As both the phosphorus and sulphur were pretty 
high in all these steel bars (Figs. 402-3 and 451), the weakening effects of 
these may account for the relatively poor showing of steel in this series of 
tests. There is no doubt, however, that the best grades of wrought iron have 
this advantage over steel, that an incipient fault or fracture does not so 
readily extend itself across the section, but is more likely to be stopped by 
the slag impurities which separate the filaments. In the more homogeneous 
and more perfectly crystallized steel a micro-flaw more readily extends 
throughout the section. 

The elastic limit seems to govern the working stress, which can be indefi¬ 
nitely repeated or reversed. If the working stress is high a material should 

















54 la 


THE MATERIALS OF CONSTRUCTION. 


be chosen which lias a high elastic limit. In general, a high-carbon steel will 
resist a continuous repetition of a high stress better than wrought iron or a 
mild steel. This is well shown in Tables XXX Ya and XXXNb, on the 
opposite page. Thus in Table XXXV a steel bars were subjected to a 
reversal of stress by rotations in a machine similar in principle to that 
shown in Fig. 454, this maximum fibre stress being 40,000 pounds per 
square inch. The steel varied from 0.24 per cent C to 0.G6 per cent C, 
and in elastic limit from 40,500 to 92,000 pounds per square inch. It will 
be seen that the number of revolutions regularly increased with an increas¬ 
ing elastic limit, and also that the hardened specimens invariably gave better 
results than the same material annealed, this being due, doubtless, to the 
higher elastic limits of the hardened specimens. These results have been 
borne out in practice by the Bethlehem Iron Co., which now uses a high- 
carbon steel (really a nickel-steel) having a high elastic limit for all its 
steam-hammer piston-rods. These do not fail where soft- and medium-steel 
rods did fail. 

This conclusion is further reinforced by Table XXXV5, in which three 
different fibre stresses were employed, on revolving shafts. While the law 
is not so uniformly exemplified, the results are sufficiently consistent to 
warrant the general conclusion that higher stresses demand higher elastic 
limits for an indefinite number of repetitions. There is now a growing ten¬ 
dency to use harder grades of steel than hitherto, both in structures like 
bridges and roofs and also in machines. And since annealing always lowers 
the elastic limit, the wisdom of such wholesale annealing as is now common 
is at least doubtful. 

It seems to the author that some internal stress is far preferable to the 
certain loss of from twenty to thirty per cent of the working strength by 
annealing. Besides, good steel is often almost ruined by bad or careless 
annealing. If a high heat is maintained for a long time, as several hours, 
the metal forms into large or coarse crystals and becomes brittle. When 
steel must be annealed, it should be uniformly, but quickly, raised to the 
required temperature and then at once allowed to cool down again. To 
both heat and cool uniformly and quickly are very difficult operations ami 
such as are not commonly performed. 


THE FATIGUE OF METALS. 


5416 


TABLE XXXVrt.—ENDURANCE TESTS OF STEEL BARS OF VARYING 

PERCENTAGES OF CARBON. 

(Watertown Arsenal Reports.) 


Kind of Steel. 

Tensile 

Strength. 

Elastic Limit. 

Extension 
in 2 Inches. 

Contraction. 

Number of 
Rotations. 

.24 C annealed. 

j 71,240 
(72,100 

40,560 

41,200 

32.3 

31.1 

59.81 

60.32 

229,300 

.24 C hardened.... 

j 74,440 
( 73,930 

45,170 

44,150 

33.15 

31.00 

69.93 

70.19 

348,000 

.42 C annealed .... 

j 80,855 
| 86,410 

44,290 

47,040 

23.00 

26.6 

56.7 

51.63 

225,900 

.42 C hardened.... 

j 92,180 
"j 89,990 

55,000 

53,170 

26.05 

26.8 

57.22 

59.88 

655,600 

.46 C annealed .... 

( 94,600 
( 98,180 

48,060 

48,060 

21.15 

21.6 

47.65 

39.83 

976,600 

.46 C hardened.. . . 

(102,880 
(104,400 

61,110 

62,130 

2£05 

22.5 

51.27 

50.42 

1,657,500 

.66 C annealed .... 

j 124,200 
( 127,720 

65,205 

65,920 

7.15 

11.95 

17.28 

20.54 

3,689,000 

.66 C hardened.... 

j 154,920 
l 153,380 

92,040 

92,040 

13.5 

13.05 

31.48 

30.15 

4,323,600 


TABLE XXXV&.— RESULTS OF ENDURANCE TESTS OF WROUGHT-IRON AND 

STEEL BARS. 

(See Fig. 401, p. 493, for the stress-diagrams of the steel bars.) 


Material. 


Wrought iron*. 

.16 per cent C steel. 
.17 “ “ 

.34 “ “ 


.55 “ 
.73 “ 

.82 “ 

1.09 “ 


a 

<c 


Number of Revolutions endured under Reversals of 
Stress on Extreme Fibre of 


40,000 lbs. 

35,000 lbs. 

59,000 

175,000 

(193,000 
(170,000 

763,000 

162,000 

970,000 

j 317,000 
( 236,000 

14,100,000 

160,000 

3,600,000 

454,000 

15,290,000 

(270.000 
] 481,000 

13,900,000 


19,150,000 


30,000 lbs. 


625,000 


12,548,000 

16 , 300 ^ 

50,000,000' 
not ruptured' 


* The average of a large number of tests. 















































542 


THE MATERIALS OF CONSTRUCTION. 


387. Limits of Maximum and Minimum Stresses for an Indefinite Number 
of Repetitions. —Wohler’s tests revealed the fact that for an indefinite 
number of repetitions of the maximum load this maximum itself could be 
increased if a portion of the stress were left on. Thus his tests on spring- 
steel, which had a static tensile strength of 124,000 lbs. per square inch, gave 
results as plotted in Fig. 458. When the load was wholly removed each 
time, the maximum load which could be repeated many millions of times 



was 67,000 lbs. per square inch, which is marked yq in the figure. When 
24,000 lbs. stress per square inch remained on each time, the maximum 
load could be raised to 75,000 lbs. per square inch, and repeated an un¬ 
limited number of times. When there was 35,000 lbs. stress left on, the 










































THE FATIGUE OF METALS. 


543 


maximum load could be raised to 86,000 lbs. per square inch ; when the 
minimum was 56,000 lbs. the maximum was 96,500 lbs., and when the mini¬ 
mum was <0,000 lbs. per square inch the maximum could be raised to 
10S,000 lbs. j)er square inch, with an indefinite number of repetitions.* In. 



Fig. 458.—Results of Wohler’s Fatigue Transverse Tests on Spring-steel. The shaded 
area is the field in which the material may be worked indefinitely. 

Fig. 458 these minimum values are plotted upon a straight inclined line, and 
the corresponding maximum values, plotted to the same scale, fall in the 
broken dotted line. 

These and many other similar series of tests on other grades of steel and 
on wrought iron led to a formula by Launhardt which may be written 

«* = ?,+“(/- P*)> .(!) 


* See also Wohler’s results in Unwin’s Testing of Materials of Construction , p. 308. 























































544 


TEE MATERIALS OF CONSTRUCTION . 


in which m = maximum stress; 

p x — “repetition limit” when n — 0; 
n = minimum stress; 
f — ultimate static strength. 

The locus of this curve is given as a full line in Fig. 458, and the area 
included between this and the minimum line is shaded, and may be consid¬ 
ered as representing the field across any part of which this material could 
be stressed and relieved an indefinite number of times. 

388. Limits of Maximum and Minimum Stresses when these are of Oppo¬ 
site Kinds. —When the stress is partly or wholly reversed an indefinite 
number of times, the working field is widened and the upper limit cor¬ 
respondingly reduced. This condition is shown in Fig. 459, the limiting 



Fig. 459. —Typical Fatigue Diagram of Limiting Stresses for 60,000 lbs. Steel for an 
Infinite Number of Repetitions or Reversals of Stress. 

case being when the stress is wholly reversed each time, when the minimum 
stress numerically equals the maximum stress. These limits are marked 
p? and —in the figure, and are here called the “reversal limits.”* 

* These terms, repetition limit and reversal limit, were coined by the author for these 
Values in his paper on this subject in Jour. Assoc. Eng. Socs., vol. vii, 1888. 


































































THE FATIGUE OF METALS. 545 

The formula for the value of the larger stress in terms of the smaller, and 
of these limits, p x and p 2 , was proposed by Weyrauch, and is 

m ~ .( 2 ) 


The loci of both of these equations are drawn in Fig. 459, and the working 
field indicated by them is shaded. Here, however, the material is supposed 
to be 60,000-lb. structural steel, and p x is taken as one half the ultimate 
strength, or 30,000 lbs. per square inch, and p 3 as one third the ultimate 
strength, or 20,000 lbs. per square inch, these being about the values of 
both of these limits as determined by all the fatigue tests which have ever 
been made. 

389. A New and Universal Formula for Dimensioning.—As shown by 
Fig. 458, a straight line would fairly fit the observed maximum stresses for 
the given minimum stresses when these also are plotted on a straight line. 
From Fig. 459, also, it would seem unreasonable to have a sudden change of 
law when the minimum stress passes through zero. Furthermore, there is 
no theoretical basis for the particular formulae, (1) and (2), which give these 
curves. It would therefore seem to be more rational, and fit the facts quite 
as well, to make these upper limits fall into a straight line, as shown in Fig. 
460. By so doing we obtain a single formula for both repeated and for 
reversed loads , whereas now two formulae are employed. To derive the 
formula for this upper limit we have, from experiment: 


Static load-limit = f = ultimate strength; 
Repetition limit = p x = \ ultimate strength; 
Reversal limit = J ultimate strength. 


Hence, when the ultimate limits are reduced to working limits, we will 
suppose that p x reduces to a, Fig. 460, and all other parts in proportion, 
giving. 


Working static-load stress 
Working live-load stress 
Working reversed stress 


— 2a; 
= a; 
= t a. 



To find the equations of the total working stress in terms of the maximum 
and minimum total stresses on any member: 

Let L — total live-load stress on any member; 

D — “ dead-load “ “ “ “ 

A — area of cross-section of the member; 

p = maximum stress in the member per square inch for both dead and 
live loads; 

a = working stress for live loads. 



546 


THE MATERIALS OF CONSTRUCTION. 


Then we have, from Fig. 460, 


nl — dead-load stress per square inch = — 
mn — live-load stress per square inch = ~ 


ml = total stress per square inch 


D 
A’ 

L 
A ; 

D + L 


■I 


= p. 





-ji 2 \/msffs/u 


mf/rm /»//' sr/tsss= fa 

CDMFHESSIUN 

t/M/r /AV COMP/fSSS/OA/^ -Jig 

Fig. 460. 


And since rs = 2a, we have, from the figure, 


V = Op = Oa + lira and hm = — (rs — 0 a); 

rs 


p = a + 



— a -f- 


D 
2 A 




• (4) 







































































THE FATIGUE OF METALS . 


547 


But A = - + 4 


V 


; hence we have 


V = « + 


and finally 




2(7) -f L) 


, or p = a 


D + L 


a 


D 4- L - 


D 


1 - 


D 


2(7) 4- L) 


V = 




1 - 


min. stress 
2 max. stress 


. (5) 


This formula may be used in place of both Launhardt’s and WeyrauclTs 
equations ((1) and (2) ), since it applies equally well to stresses of the same 
or of opposite kinds, by paying attention to the sign of the minimum stress. 
When the minimum stress becomes negative the sign of the second term in 
the denominator changes to plus, thus reducing p below a. 

Another argument in favor of this formula lies in the fact that it is the 
same as the old rule of using twice the factor of safety for live as for dead 
loads, as will now be shown. 

With the same notation as above, we have 


also 


L D_ 2L + D 
a 2 a 2 a 


L + D 


Substituting the value of A , we have 


2a(L 4- 7))_ a 

~YL~+iy ~ " 7) 

'2(7, 4- D) 


a 

min. stress 
2 max. stress 


( 6 ) 


We find, therefore, that the past practice founded on experience, and the 
fatigue experiments, all agree and are all expressed in this one formula which 
is universal in its application to stresses of the same and of opposite signs. 
Its use is more laborious than those hitherto used, as given in equations (1) 
and (2), only in requiring a division in place of a multiplication; but as such 
work is now done wholly by the slide-rule, even this objection is removed. 


















CHAPTER XXVIII. 


STRENGTH OF THE COPPER-ZINC-TIN ALLOYS. 

COPPER. 

390. Strength of Copper. —The first and most general error to guard 
against in the matter of the strength of copperand its alloys is that of ignor¬ 
ing the mechanical treatment to which the material has been subjected. 
Thus in the .case of copper plate, as shown by Fig. 4G1, a hot-rolled plate 
lias an elastic limit of only some 7000 or 8000 lbs. per square inch, with an 
elongation of 50 per cent, while the same plate, cold-hammered, has an 
elastic limit of over 20,000 lbs. per square inch, with an elongation of 30 per 
cent. Both have an ultimate strength of about 33,000 lbs. per square 


3qm 


3 

O 5/0/5 20 25 30 35 50 55 50 

Fig. 4G1.—Typical Stress diagrams of Copper Plate 4 in. thick. 

(Martens, Berlin Testing Lab. Communications, 1894.) 

inch. When simply cast, without rolling or forging, both the elastic limit 
and the ultimate strength are much less, but copper is seldom or never used 
in this way. 

Drawn copper wire has an elastic limit of about 25,000, with an ultimate 
strength of some 35,000 lbs. per square inch, as shown in Fig. 4G2, with an 
elongation of about 30 per cent. 

If the strength of copper be computed on the actual section at all stages 
of the test, and if the strength so computed be plotted to the diminishing 
cross-section, the results will plot in a straight line, as shown in Fig. 463. 

548 






















STRENGTH OF THE COPPER-ZINC-TIN ALLOYS. 


549 



Fig. 462.—Typical Stress-diagram of Drawn Copper. {Wat. Ars. Rep. 1886, 

vol. ii. p. 1673.) 



Fig. 463.—Showing a Linear Relation between Reduction of Area of Section ana Stress 
per Square Inch of Actual Section of Rolled Copper Plate i inch thick. {Rep. h\ 
Com., vol. hi, PI. VI.) 





















































550 


THE MATERIALS OF CONSTRUCTION. 


That is to say, when copper is cold-drawn, its strength per square inch 
regularly increases up to rupture, when its strength per square inch of actual 
section is some 70,000 lbs. per square inch. 

391. Annealing or Softening Hard-drawn Copper Wires or Plates. 
Unlike steel, copper is softened by quenching in water from a sufficiently high 
temperature. The softening effect is due, however, rather to the tempera¬ 
ture attained than to the manner of cooling. At least the sudden cooling 
does not prevent the softening. The annealing temperature is about 
750° F., as shown in Fig. 464. 



Fig. 464. —Effects of Heating to given Temperatures, and then Quenching in Water, 
Hard-drawn Copper Wires. (Martens, Berlin Testing Lab., 1894, PI. I.) 

392. The Strength of Brass. —Brass is an alloy of copper and zinc. The 
mechanical properties of all possible compositions are given in Fig. 465, 
these applying in a general way to cast forms only. Either hot or cold forg¬ 
ing or rolling will greatly change these properties. Thus the strength of 
very hard-drawn brass wire or hard-rolled brass plate may have a tensile 
strength of over 60,000 lbs. per square inch, with an elastic limit about the 
same, as shown in Fig. 466. Annealed brass plates or wires, however, have 
an elastic limit of only about 10,000 lbs. per square inch. 

Brass is much harder than copper, as shown in Fig. 465, by the “ crush¬ 
ing strength ” diagram, this rising from 28,000 lbs. for 100 per cent copper 
to 120,000 lbs. per square inch for 50 per cent copper. It is this property 
of increased hardness which makes brass so much more useful than copper 
in the arts. The conductive capacity of brass is, however, much less than 
that of pure copper, it falling from 0.90 for pure copper to 0.20 for 70 per 
cent copper. 



















STRENGTH OF THE COPPER-ZING-TIN ALLOYS. 


551 



Fig. 465.—Properties of Cast Brass for Varying Proportions of Copper and Zinc. The 
“composition” argument gives the proportions of copper. (Data from U. S. Test 
Board Rep. 1881, vol. n.) 



Fig. 466.— Stress-diagrams of Rolled Plate of Brass and Copper, having the Composition 

Cu 67, Z 33. ( Fr. Com. Rep., vol. hi, PI. V.) 






















































552 


THE MATERIALS OF CONSTRUCTION. 


The most generally useful brass composition is from 60 to 70 per cent 
copper and 40 to 30 per cent zinc, as is fully shown by Fig. 465. 

By rolling to thin plates, especially by cold-rolling, the strength of brass 
may be greatly increased at the expense of the ductility. The simultaneous 
qualities of strength and ductility which may be expected from brass which, 
in the form of a casting, has a tensile strength of 35,000 lbs. per square inch 


MM 


som 


70000 


sqm 




























' 









r 

§r 


=53 
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'V' 

< 

. 





s 

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'vr 

020 


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O /a SO SO 40 SO SO 70 

Fig. 467. —Showing the Relation between the Ultimate Strength and the Ultimate 
Elongation of Brass. (Fr. Com. Rep., vol. in, PI. V.) 


and an elongation of nearly 40 per cent are given in Fig. 467. Thus in a 
ribbon £ in. X i in. in cross-section the strength is 45,000 lbs. per square 
inch with 60 per cent elongation; 60,000 lbs. with 15 per cent elongation; 
and 90,000 lbs. with 3 per cent elongation. 

393. The Strength of Bronze. —The ultimate tensile strength of all possi¬ 
ble compositions of copper, zinc, and tin, in the form of unworked castings, 
is given in Fig. 468.* This is similar to that first published by Dr. Thurs- 


* This is the same as Fig. 76, which is repeated here for convenience. 



























STRENGTH OF THE G0PPER-ZIN0-T1N ALLOYS. 


553 


ton, but his was constructed from torsion tests, while this is made wholly 
from tension tests. It is the property of any equilateral triangle that the 
sum of the normals from any point in it to the three sides is equal to the 
common altitude of the triangle. Hence if these altitudes be each made to 
represent percentages, from zero to 100, and so graduated, each starting 
with 100 at the apex and reducing to zero at the opposite base, these may 
each represent a scale of one of the three ingredients, copper, zinc, and tin, 



T//V Z///C 


Fig. 468.—Showing the Tensile Strength, in Pounds per Sq. Inch, of All Possible Com¬ 
binations of Copper, Tin, and Zinc, in the Form of Unrolled or Unforged Castings. 
(Compiled by the Author from the Records of the U. S. T*est Board 1881.) 

which go to make up all the bronzes. By drawing lines through these points 
of division in the altitudes, parallel to the bases, the triangle is subdivided 
into a series of similar smaller triangles as shown in Fig. 468. Any possible 
composition of copper, tin, and zinc, each represented as a certain per¬ 
centage of the whole, may now be represented graphically by a location on 
this diagram. Its normal distances from each of the three sides, read off on 
the section lines in percentages, are at once the percentages of these three 
ingredients in that composition, the sum of these, of necessity, always 
being 100. 

















554 


THE MATERIALS OF CONSTRUCTION. 




Fig. 469. —Results of Tension and Compression Tests on Three Alloys used for Valve* 
stems. Tobin bronze rolled, others plain castings. (Russell, Jour. Assoc. Eng. Soca. % 


vol. xv, p. 207. Tests made by the Author.) 

/ 

60000 

• 

50000 

50000 

gym 

a 

^ fh 

uleo, / 

WEEEC 

£ FFOA 

-e— 


\ 


FFL 











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^ 






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• 




• 


1 

k P£ 

'EC£N. 

r /U?£ 

OF 

EiO/V 

OAT/O 

4/ 


I? S /0 & 20 25 SO SS 


Fig. 470. —Tension Stress-diagrams of Cast and Rolled Bronzes. {Wat. Ars. Rep. IS 15.) 






















































































STRENGTH OF THE COPPER-ZINC-TIN ALLOYS. 


555 


44000 

% 


70000 
' ^ 

#0000 

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sq000 


% 


s 

I 

$ 




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—SX- 

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>M3/s > fii//3 l 5'zi.53ZzZi33'/3 

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Xji.gsi./^u.oo 

M./0, Pi./fy Cb.S896 
XMyfySi.tyOuS/fe 


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r 3//55 

Sr ^ 

CA/r 0/ 

' fCOA, 

ff/WVA/ 

0/V /S5 

'■is/vffr, 

Z? 


^ 5 /I? /5 20 25 30 35 

Fig. 471.—Tension Stress-diagrams of Aluminum Bronze of Various Compositions, 
Cast in a chilling and in dry-sand moulds. ( Wat. Ars. Rep. 1888.) 



Fig. 472.—Strength of Aluminum Bronze at Various Temperatures and for Various 

Percentages of Elongation. 





























































o56 


THE MATERIALS OF CONSTRUCTION. 


From an examination of this chart it is at once evident that only those 
alloys near the copper apex are of any value, the strongest being, however, 
near the copper-zinc side, where the composition is about 59 per cent copper, 
39 per cent zinc, and 2 per cent tin. The tensile strength of such a casting, 
if properly made, is about 60,000 lbs. It is too brittle, how r ever, to be of 
much value. The most valuable alloys are those having an ultimate strength 
of from 35,000 to 40,000 lbs. tensile strength, this having from 20 to 30 
per cent elongation. This is found in the vicinity of 75 to 85 per cent 
copper, 17 to 5 per cent zinc, and 8 to 10 per cent tin. 

Tobin Bronze is simply such a composition as the above hot-rolled after 
casting. The effect of this rolling is to greatly increase both the strength 
and the ductility, as shown by Fig. 469.* This material is in almost every 
respect similar to soft steel, so far as its mechanical qualities are concerned. 
It has the further advantage of not corroding under ordinary conditions, 
hence its extraordinary value as a structural material. The author has seen, 
however, some very remarkable and unexplained fractures of this material 
which leads him to suspect its reliability. 

Phosphor-bronze has no special mechanical properties other than marks 
all good bronzes (see Fig. 470). Phosphorus is used to destroy the effects 
of oxidation in melting rather than to add to the strength or ductility other¬ 
wise. In destroying these oxides it does improve the product; but if the 
melting is performed in such a way as to prevent oxidation, there is no need 
of the phosphorus. 

394. Aluminum-bronze may have great strength in Doth the cast and 
the rolled forms, as shown in Fig. 471, where many tests on different 
compositions and from different kinds of moulds are plotted from the same 
origin. The effect of the rolling in increasing the strength and the ductility 
is evident. A small percentage of aluminum is thus seen to greatly improve 
the bronze although its strength alone is very small, as is also shown in this 
figure. 


* The total elongation, which was over 30 per cent, is not shown in this figure. 




CHAPTER XXIX. 


THE EFFECTS OF TEMPERATURE ON THE MECHANICAL PROPERTIES 

OF METALS. 

EFFECTS ON IRON AND STEEL. 

395. As Shown by Stress-diagrams. —This subject has been very fully 
and carefully investigated at the testing laboratory of the U. S. Arsenal at 
Watertown, Mass., and a full series of diagrams, similar to that shown in. 



Fig. 473.—Stress-diagrams of Steel Bars, 0.20$ Carbon, 0.45$ Manganese, at Various 

Temperatures. (I Vat. Ars. Rep. 1888.) 

Fig. 473, is given in the report for 1888. The curves in this figure exhibit 
the action of 0.20 per cent carbon steel, having a normal tensile strength at 
70° F. of 70,000 lbs. per square inch, with a normal elastic limit of some 37,000' 
bis. per square inch. Fig. 473 reveals both the elastic limit and the ultimate 

557 




































558 


THE MATERIALS OF CONSTRUCTION. 


strength, both of which are above the normal at 0° F., and below the normal 
at 210° F. The ultimate strength then increases with a rising temperature, 
reaching a maximum at about 600° F., from which temperature it regularly 



Fig 474.—Variation of Teusile Strength will) Temperature. {Wat. Ars. Rep. 1888. 



diminishes in ultimate strength, reaching 60,000 lbs. at 800° F., 50,000 lbs. 
at 960° F., 40,000 lbs. at 1050° F., 30,000 lbs. at 1150° F., 20,000 lbs. at 
1400 c F., and 10,000 lbs. at 1570° F. These simultaneous values are better 















































































EFFECTS OF TEMPERATURE ON METALS. 


559 


read off from Fig. 474 than from Fig. 473. In the former, also, are found 
the variations of the ultimate strength of all grades of steel, and of wrought 
and cast iron. 

Returning now to Fig. 473, it will be seen that the elastic limit regularly 
and continuously diminishes from the zero temperature , where it is some 
42,000 lbs. per square inch, the metal becoming regularly more plastic as 
the temperature rises. This is also shown in Fig. 478. 

In Fig. 476 we see the relative effects of slow and rapid applications of 



Fig. 476.—Ultimate Tensile Strength of Steel and Wrought Iron at Temperatures 
between Freezing and 1000° F. for Slow and Rapid Loading. ( Fr. Com. Rep., 
vol. ii, PL XX.) 


the load on wrought iron and steel at different temperatures. At ordinary 
temperatures the quick loading develops a greater ultimate tensile strength 
than the slow loading. Between 250° and 700° F. for steel, and between 
150° and 500° F. for wrought iron, the quick loading gives a less ultimate 
strength, while beyond these higher temperatures the quick loading .again 
gives the greater strength. 


L - Y/EIOPO/HT 
R=ULT/M/1T£ STRENGTH 
LtfSlOW lO/W/NG- 
l 2 /? 2 T7Af£mfflW6 /AfW. 
ff* T/ME0f{MmG2T03S£C. 



-/$?£ ~/0O° SO 9 0° i-SO 
Fig. 477.—Tension Tests of Soft Steel Wire at Temperatures from — 90° to -f- 200° F 
for Different Rates of Loading. (Fr. Com. Rep., vol. ii, Plate XX.) 


Similar effects are shown in Fig. 477 for soft steel wire, for both the 
ultimate strength and the yield-point or apparent elastic limit, for tempera¬ 
tures between — 90° and -j- 200° F. 












































560 


THE MATERIALS OF CONSTRUCTION . 


396. The Change in the Elastic Limit is by far the most important of 
all the changes produced by rising temperatures, so far as structural use is 
concerned. Commonly only the ultimate strength is given for rising tem¬ 
peratures, and as this increases up to 500° or 600° F., it is assumed that the 
working strength increases also. That this is not the case is shown for one 
grade of steel in Fig. 473, and for all grades of steel combined in Fig. 478. 
Here the “ mean variation in the elastic limit ” curve continuously descends 


30%> 


20 
/O 
0 

O 200 OOO OOO 800 /OOO /200 0400 

Fig. 478.—Grand Mean Curves from Temperature Tests on Steel Rods 0.8 in. in diam¬ 
eter, turned from lpin. rods, of ten different degrees of hardness, from 0.0% to 
0.97$ C. (Wat. Ars . Rep. 1888, p. 245.) 

from a zero temperature, the mean results falling almost exactlv in a smooth 
curve, which is nearly a straight line, while the “ mean ultimate strength ” 
curve has a minimum point at 200° F. and a maximum point at 500° F. 
after which it regularly decreases also. Thus at 500° F. the mean ratio of 
elastic limit to ultimate strength, for all grades of steel, is only 0.36, while 
at ordinary temperatures, from zero to 100° F., it is 0.57, as shown by Fig. 
478. 

For structural purposes , therefore , the working strength of wrought iron 
and steel must be regarded as regularly diminishing , while the temperature 
increases , the rate of diminution being about 4 per cent for each 100° F. 
increase in temperature. 

Similar curves in Fig. 479 do not indicate this uniform reduction from 
a zero temperature, but they are not based on as extensive a series of tests as 
those summarized in Fig. 478. 




















EFFECTS OF TEMPERA TUBE ON METALS. 


561 


397. The Change in Ductility. —The great reduction in the elongation 
of wrought iron and steel, for temperatures from 100° to 400° F. with a 



Fig. 479.—Tensile Properties of Wrought Iron aud of Open-hearth Steel at Various 
Temperatures Centigrade. (Berlin Testing Lab. 1898.) 


minimum at about 300° F., is a remarkable fact which could not have been 
predicted. Thus wrought iron with 22| per cent elongation at a tempera¬ 
ture of 80° F. has but 7 per cent elongation at 300° F., as shown in Fig. 



Fig. 480.—Variation in the Ductility of Wrought Iron and Tool-steel for Varying Tem¬ 
peratures. Cornell University Tests. (Jour. West. Soc. Engvs., vol. i.) 
















































562 


THE MATERIALS OF CONSTRUCTION. 


480, while from Fig. 479 a 32-per-cent elongation of both wrought iron and 
mild steel at 32° F. reduces to 14 per cent at 300° F. Above this tempera¬ 
ture the elongation increases again, reaching its normal amount at a tempera¬ 
ture of some G00° F. 


k 

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£ 

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£ 







Jif 


zsmm 


/smm 


Fig. 481. —Effect of Moderate Temperatures on the Modulus of Elasticity. ( Wat. Ars. 

Rep . 1887.) 

398. The Change in the Modulus of Elasticity is shown in Figs. 479 and 
481. In all cases it regularly decreases for rising temperatures, except that 
the Berlin tests on steel, Fig. 479, show a small increase in the modulus 


Z820 


zm 


zm 


7.7M 


/ 







X 





K 





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) / 

£ 

_ 





| 

A 




1/ 






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£=£l 

'T£ //t 
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?7 



2 <3 4 S 6* 

Fig. 482.—Variations in the Specific Gravity of Steel at Different Temperatures. Each 
point the mean of six observations, the carbon varying from 0.53^ to 1,08^ 
(Langley, in Am. Chem., 1876.) 




























































EFFECTS OF TEMPERATURE ON METALS. 


563 


r 

! 



Fig. 453.—Hot Tests of Wrought-iron Car-axles. Temp. 300° F. 



Fig. 484.—Cold Tests of Wrought iron Car-axles. Temp. — 18° F. 


Impact Tests of Car-axles, 4J in. in Diameter, showing Characteristic Fractures at 
300° F. and at — 18° F. (Thos. Andrews, M. Tnst. C. E. r before the Soc,. Engn. 
'London) ; 1806, in a Bessemer Premium Paper.) 




















564 


THE MATERIALS OF CONSTRUCTION. 


from freezing to 200° F. No such effect is shown in Fig. 481. In general 
it may be said that for wrought iron and steel the modulus of elasticity 
decreases about 2 per cent for each 100° F. increase in temperature. 

399. Effect on Specific Gravity.—This is shown in Fig. 482 to he quite 
uniform, but no absolute temperatures were determined. We can only say 
that in cooling from a white heat to black the specific gravity increased from 
7.7G to 7.83, an increase of nearly one per cent variation in temperature.* 

400. Effect on Resistance to Impact.—This is shown, for wrought-iron 
car-axles, in Fig. 485, and the change in the fracture from a crystalline 
appearance at a temperature of — 18° F. to a fibrous appearance at 300° F. 
is well shown in Figs. 483 and 484. The minimum toughness is found at 
300° C. or 570° F., which agrees substantially with the temperature of maxi¬ 
mum ultimate tensile strength, but of minimum elongation. This could 
have been predicted from the reduced ductility at this temperature. The 
paper here cited contains a great many photographic reproductions of frac¬ 
tures from which those in Figs. 483 and 484 have been selected as character- 


are all very much alike. 

Mr. Andrews’s impact tests of wrought-iron car-axles at zero and at 
100° F. show a great difference in the resistance to impact even for this 


istic. They 



Fig. 485.— Endurance Tests of Wrought-iron Railway axles at Varying Temperatures 
Centigrade. Axles deflected by impact and then turned over and deflected in the 
opposite direction. (Andrews, before the Soc. of Engrs. (London), 1896.) 


small variation in temperature.* These axles were 4^ in. in diameter and 
rested on supports 3| ft. apart. They were tested by dropping a tup 
weighing 2240 lbs. a distance of 30 in., the axle being turned over after each 
blow and its temperature restored, until it ruptured. 

These tests serve also to emphasize the fact that wrought iron is an 
extremely variable material when forged in large masses, and by no means as 


* From Proc. Inst. Civ. Eng., vol. xciv. p. 209. 

















EFFECTS OF TEMPERATURE ON METALS. 


565 


TABLE XXXYI.—ANDREWS’ TESTS ON WROUGHT-IRON CAR-AXLES AT 0^ 

AND 100° F. 


Cold Tests at 0° F. 

Warm Tests at 100° 

F. 

Number of 
Axle. 

Sum of all Deflec 
tions of Axie 
in Inches. 

Total Number 
of Blows caus¬ 
ing Fracture. 

Number of 
Axle. 

Sum of all Deflec¬ 
tions of Axle 
in Inches. 

Total Number 
of Blows caus¬ 
ing Fracture. 

44 

4.8 

8 

45 

13 3 

23 

46 

5.7 

8 

47 

11 9 

15 

48 

0.8 

2 

49 

19 9 

23 

50 

6.6 

8 

51 

14.4 

17 

52 

8.7 

11 

53 

21 7 

22 

54 

38.6 

44 

57 

71.1 

107 

55 

4.5 

6 

63 

9.1 

12 

56 

6.9 

10 

64 

31 4 

49 

58 

7.2 

9 

65 

32.1 

44 

59 

5 3 

7 

67 

40.9 

54 

60 

4.0 

6 

69 

17.9 

24 

61 

10.3 

14 

70 

16.4 

22 

62 

5.6 

8 

71 

47.5 

66 

66 

25.7 

33 

72 

43.8 

62 

68 

26.2 

32 

73 

37 5 

57 

77 

21.6 

29 

74 

25.9 

34 

78 

66.0 

84 

75 

12.1 

16 

79 

58.8 

76 

76 

17.2 

25 

80 

49.4 

64 

81 

17.8 

22 

83 

25.9 

34 

82 

23.4 

35 

84 

30.1 

42 

89 

24.5 

32 

87 

25.3 

32 

85 

34.4 

35 

88 

3.4 

5 

86 

10.6 

56 

90 

16.1 

20 

111 

34.6 

53 

91 

35.4 

48 

98 

52.8 

78 

92 

8.6 

12 

113 

30.4 

45 

93 

7.4 

10 

120 

23.1 

32 

94 

3.4 

5 

103 

34.5 

49 

95 

3.0 

5 

121 

25.9 

40 

96 

31.2 

43 

108 

41.1 

54 

Average 

18.2 

23.8 

Average 

27.9 

37.1 


uniform as mild steel. If steel axles would show one half as great a range 
in results as is here revealed for wrought iron, they would all be rejected 
without any hesitation. 


EFFECTS ON COPPER AND BRONZE. 

401. Effects on Copper.—These are shown in Fig. 486. Both the elastic 
and the ultimate strength regularly diminish for rising temperatures, while 
the elongation remains nearly constant up to 600° F. The modulus of 
elasticity rises to a maximum at the boiling temperature, where it is 15 per 
cent higher than at a freezing temperature, and then rapidly declines. The 
elastic-limit strength of rolled copper may be said to diminish at the rate of 
5 per cent per 100° F. increase in temperature. 


































566 


THE MATERIALS OF CONSTRUCTION. 


402. Effects on Bronze.—The elastic strength, the ultimate strength, 
and the ductility of bronze are but little affected by rising temperatures up 
to 600° F., the reduction in strength being only about 2 per cent per 100° F. 



Fig. 486.—Tensile Properties of Copper and Delta metal at Various Temperatures 

Centigrade. (Berlin Testing Lab ., 1893 ) 


within this limit, as shown in by Fig. 487. The modulus of elasticity rises 
some 20 per cent at 550° F., and then rapidly falls. 

20 


70 

00 

SO 

40 

30 

20 

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SIM, 

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wt\ 


\ F 

$ 

0^/1 /X 







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mo 

8000 

7000 

oooo 


MANGANESE BRONZE. DELTA-METAL (ROLLED). 

Fig. 487.—Tensile Properties of Manganese Bronze and Delta-metal (rolled) at Various 
Temperatures Centigrade. (Berlin Testing Lab., 1893.) 






































EFFECTS OF TEMPERATURE ON METALS. 


567 


403. Effects on Delta-metal. —These are shown in Figs. 486 and 487 for 
cast and rolled delta-metal respectively. The ultimate strength falls much 
more rapidly than the elastic limit, this remaining nearly constant up to 
about 500° F. The modulus of elasticity falls rapidly after passing 300° F., 
but the ductility increases to 400° F. for rolled, and to 550° F. with the 
cast, metal, the elongation being 60 per cent and 55 per cent respectively at 
these limits. 

404. Conclusions. —In general it may be said that copper and its useful 
alloys have their mechanical properties changed but little for the variations 
of temperature ordinarily occurring in the use of these materials in the arts. 
See Fig. 472 for aluminum bronze. 

For very low temperatures the static strength of iron and steel increases 
somewhat, but both elastic limit and elongation, or ductility, decrease, so 
that the resistance to shock is considerably reduced. The bad effect of cold 
weather, therefore, is shown on materials subjected to heavy blows, like 
railroad rails. It is not practicable to make shock tests at temperatures lower 
than that found out-of-doors in winter, or such as maybe created in a large 
refrigerating warehouse. Tests at extremely low temperatures, therefore, 
such as shown in Fig. 477, are necessarily limited to tension tests of small 
specimens, which can be surrounded by a cooling apparatus. 

If shock tests are made on artificially cooled bars, at ordinary tempera¬ 
tures, they should be returned to the refrigerator after each blow, or at 
most after each second blow. 

The curves shown in Figs. 474 to 480 show that in tension tests at 
ordinary atmospheric temperatures no note need be made of the particular 
temperature of the test bar. It is very different, however, with impact 
tests as shown for wrought iron in Fig. 485. Here even these atmospheric 
variations are important and the temperature should always be noted. In 
order to make such tests comparable they should be made at about the same 
temperature, and 60° to 70° F. has been selected as the standard. Most 
kinds of test-specimens could be brought to this temperature by immersion 
in water. 


CHAPTER XXX. 


RESULTS OF TESTS ON CEMENTS, CEMENT-MORTARS, AND 

CONCRETES. 

TENSILE AND COMPRESSIVE STRENGTH OF CEMENTS AND CEMENT MORTARS. 

405. Tensile Strength of Natural Cement.—As shown in Art. 315, Fig. 

337, the tensile strength of cement is a true index of its compressive strength. 
It was also stated in Art. 155 that the American natural cements are, as a 
class, of a superior grade, and that they are quite sufficient in strength for 
nearly all purposes for which cement is required. Occasional failures of this 
class of cements has, however, developed an undue popular prejudice against 
them. If reasonable precautions were exercised in testing such cements, a 
great deal of money could be saved with no prejudice to the works on which 
it might be used. 

Fig. 489 contains the average results of many thousands of tests of 



Fig. 489.—Average Results of Time Tests on Rosemlale cement Mortar. (Boston Main 

Drainage , 1885, p. 121.) 

Rosendale-cement mortars, extending over the several years of the construc¬ 
tion of the Boston Main Drainage works. The usual mixture for natural- 
cement mortar is 1 C. : 2 S., and these tests give for this mortar an average 
tensile strength of 180 lbs. per square inch at the end of one year. In Fig. 

568 































TESTS ON CEMENTS, CEMENT-MORTARS , AND CONCRETES. 561) 

490 this mixture had, in tests made during the construction of the Cairo 
bridge across the Ohio River, for Milwaukee cement, 160 lbs.; for Utica 
cement, 145 lbs.; and for Louisville, 140 lbs., this strength having been 
reached in each instance at the end of three months. 



Fig. 490.—Time Tests on Three Standard Natural-cement Mortars. (Jour. Assoc. Eng . 

Socs., vol. IX.) 

Long-time tests of Louisville-cement mortar mixed the same as is usual 
with Portland cement, 1 C. : 3 S., gave at one year an average tensile 
strength of 230 lbs. per square inch, as shown by Fig. 491. This greater 
strength is probably due to the superior methods of making the test bri¬ 
quettes which have been followed in this department for many years. This 








































































570 


TEE MATERIALS OF CONSTRUCTION. 


figure shows the average strength of neat Louisville cement to be 500 lbs. 
per square inch in one year when mixed on the “jig/ a kind of milk¬ 
shake” apparatus, described in Engineering News , vol. xxv. p. 3 (Jan. 3, 
1891). 



Fig. 491.—Average Results of Time Tests ou Eight Brands of Louisville Cement. 

(St. Louis Water-works, 1896.) 


Similar results have been obtained in the tests of natural cement made in 
connection with the building of the new Sault Ste. Marie Canal lock, as 
shown in Fig. 492. Here one brand of natural-cement mortars gave at one 



Fig. 492.—Strength of One Brand of Natural-cement Mortar. (Wheeler, Rep. Chf. 

Engrs. 1894, p. 2852.) 






















































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 571 


year, for 1C. : 1 S., 500 lbs.; 1 C. : 2 S., 370 lbs.; and 1 C. : 3 S., 200 lbs. 
tensile strength. An average of five brands of natural-cement mortar, 
1C. : 1 S. gave at three months 380 lbs., and an average of ten brands of 



Fig. 493. —Strength of Natural Cement Neat and 1 C. : 1 S. (Wheeler, Rep, Chf. Engrs . 

1895, p. 2983. ) 


natural cement neat gave at six months 410 lbs. tensile strength, as shown 
in Fig. 493. 

These results all go to show that if reasonable care be exercised in 



Fig. 494.— Average Itesults of Time Tests on Portland-cement Mortar. {Boston Main 

Drainage, 1885.) 







































































572 


TEE MATERIALS OF CONSTRUCTION. 


inspecting and testing the cement, the standard American natural cements 
are abundantly strong for a large proportion of the work requiring the use 
of such material. 

406. Tensile Strength of Portland Cement. —The average results of tests 
on Portland cement made on the Boston Main Drainage works are given in 
Fig. 494. Comparing this figure with Fig. 489, we may say that 4 to 1 of 
Portland cement is fully equal to 2 to 1 mortar of natural cement. Similarly, 
from these same figures we may say that neat Portland cement at one year 



Fig. 495. —Average Tensile Strength of Fifteen Brands of Portland Cement. (St. Louis 

Water Dept., 1896.) 

is 60 per cent stronger than neat natural cement, and that standard mortar 
composed of 3 S. : 1 C. is nearly twice as strong when made of Portland 



Fig. 496.—Results of Cement Tests made at the Iowa State University. 


cement as when made of natural cement. Similar results on neat cement 
are shown in Fig. 496. 

In Fig. 497 are shown Tetmajer’s average relations of the strength of 
standard natural- and Portland-cement mortars at various ages up to one 
year, as percentages of the strength at 28 days. From this it appears that 
natural-cement mortar at one year is twice as strong as it is at 28 days, 
while Portland-cement mortar at one year is only 50 per cent stronger than 
at 28 days. Furthermore, the strength of the natural cement is still increas¬ 
ing, while that of the Portland cement has about reached its maximum. 





























































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 573 


In Fig. 498 are given the average results of tests on nine brands of 
Belgian Portland cement and on twelve brands of English Portland, both 
neat and 1 C. : 3 8. It would seem these mortar results are too low in 



Fig. 497.—Average Relation of Strength of Cement-mortars which have Hardened 
under Water for periods less than One Year to the Strength of Twenty-eight Days. 
(Tetmajer’s Communications, vol. vi. pp. 379-389.) 


comparison with the results on the neat cement. In general standard mor¬ 
tar, 1C. : 3 S., should reach one half the tensile strength of the neat cement 
at the end of a year. The strength of Portland cement, both neat and with 


m 


000 


400 


000 


0 




r 

ian CEt 


//TAT 


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$ 

£ 




/A 

( 

0 

/t/i 

9 


0 /00 200 200 000 
Fig. 498.—Average Results of Tension Tests on Belgian and English Portland Cements. 
(Allison, Trans. Can. Soc. C. E ., vol. ix, 1895, p. 296.) 

























































574 


THE MATERIALS OF CONSTRUCTION. 


sand, continues to increase for many years, as appears from Fig. 499. Here 
the strength of the standard mortar, 10. : 3 S., was 65 per cent of that of 
the neat cement at one year, while at five years it had increased to 75 per 
cent of the strength of the neat cement at that age. Short-time tests on 



Fig. 499.—Long-time Tests of American and Foreign Portland Cements. Figures give 
number of tests averaged. {Jour. Assoc. Eng. Socs., vol. xv. p. 193, and Can. Soc. 
C. E., vol. ix.) 

sand mixtures always give a much low r er ratio of strength to that of the same 
cement neat than long-time tests. It will be observed, also, that the five- 
year tests in Fig. 499 were on an American cement. There is now no ques¬ 
tion as to the superior quality of many brands of American Portland cement. 
This is also shown by Fig. 500. In this figure the ratio of the strength of 
the mortar is so low as to lead to the conclusion that no special pains were 
taken to compact the briquettes. The strength of cement-mortar, 1 C. : 
3 S., can readily be increased 100 per cent by mixing somewhat dry and 
using the Bohme hammer, Fig. 352, as compared to the strength of soft 
mortar which is merely pressed into the moulds. It is for this reason that 
American engineers adhere so uniformly to the neat test, the strength of 
neat briquettes not being so much affected by the method used for filling the 
moulds. 

The relative effects of hardening in air and in water are shown in Fio-. 

o O 

502 for one brand each of natural, slag, and Portland cement. Evidently 
the continued presence of water is essential to the greatest strength of the 
Portland cement, while the natural cement reached a higher strength in the 
air. 














































































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 575 


* nixture ° f natUral and Portland cemen t varies in strength between 
that of the true ingredients, strictly in proportion to the percentage of each 
used, as shown by Fig. 503. 

A mixture of IS. : 1 C., if the mixing be very thorough, has about the 
same tensile strength as the same cement neat. (See Fig. 490.) 



Fig. 500. —Average Tensile Strength of a great many Samples of One Brand of Ameri¬ 
can Portland Cement (189G). (Robt. W. Hunt & Co.) 


407. The Modulus of Elasticity of Portland-cement Mortars. —These are' 
shown in Fig. 504 for two brands of Portland cement and one brand of slag- 
cement. The modulus increases with age, as would be expected, but it is- 
also one third greater for standard mortar, 1 C. : 3 S., than it is for the neat 
cement, which could hardly have been predicted, especially when determined 
from a cross-bending test. The modulus is very much lower for the slag- 
cement than for the Portland cement; in other words, the slag-cement is: 
more elastic, or resilient, than the Portland. This is an important quality 



































576 


THE MATERIALS OF CONSTRUCTION. 


which should be further studied. The moduli of elasticity in compression 
of neat-cement mortars, and concretes are given in Art. 418, Figs. 546, 
547, and 548. 



408. Strength of “ Sand-cement ” Mortars. —Within a few years a new 
product has been introduced (from Denmark), composed of Portland cement 
reground with sand. This is a pure dilution, but it also makes available, by 
regrinding, the coarser particles of the cement, so that the new mixture may 






































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 577 ' 

now be mixed again with raw sand, the same as the pure cement, and the 
result is a considerable cheapening of the product for a given final strength. 
Thus if three parts of sand be ground with one part of Portland cement, the 



Fig. 502.—Relative Strength of Cement-mortars when Hardened in Air and in Water. 

(Tetmajer’s Communications , vol. vi.) 

product is four parts of “ sand-cement.” If now this be incorporated with 
raw sand in the proportion 1 : 3, we shall have to use 12 parts of raw sand, 

















































678 


THE MATERIALS OF CONSTRUCTION. 


making in all 15 parts of sand to 1 of cement. The formula for this mortar 
would be, therefore, 1:3:12 = 10. :15 S. The tensile strength of 


JW 


4W 




Sr 

WfA 

'T/I/?. 

T TT 

AMi 


' /?£/ 

vm 

t 

-L _ 

7? 

A 

* 










X 










*5 










§_ 










m 

6 

9 

6 

9 

* 

9 


9 

0 


/?.. £'0 40 00 S 0 . / 0 ff 

Tig. 503.—Strength of Mixtures of Natural and Portland Cement. Average of testa, 
from one week to one year. (Wheeler, Rep. Chf. Engrs. 1894, p. 2850.) 


various such mixtures, at ages up to one year, are given in Fig. 505, in com¬ 
parison with the strength of standard mortar 1 C. : 3 S. Thus the mixture: 
1 : 2 : 6 = 1 0. : 8 S. gives almost as great strength as the ordinary 1 C. : 3 S*. 



Fig. 504.—Modulus of Elasticity of Portland-cement Mortar as determined by Cross- 

bending Tests. (Inst. Civ. Engrs., vol. cxx. p. 375.) 


In Fig. 506 both the tensile and the compressive strengths of sand-cement 
mixtures are given from 1 C. : 3 S. to 1 : 3 : 8 = 1 C. : 35 S. In Fig. 507 
these same results are plotted to the argument cement 4- total sand and 
cement. 























































TESTS ON CEMENTS , CEMENT-MORTARS, AND CONCRETES. 579 


In Fig. 508 the tensile and the compressive strengths are given for a 

constant total ratio of sand to cement, but with different ratios of ground to 
unground sand. 

While “ sand-cement ” is now (1897) manufactured at New York City, 
it is doubtful if it ever comes to be used very much in America, since it 



Fig. 505.—Strength of Sand-cement Mortar. The first figure denotes parts of Port¬ 
land cement ; the second, parts of ground sand; the third, parts of unground sand. 
( Engr . News, April 16, 1896, vol. xxxv. p. 254.) 

cannot compete in price with our excellent natural cements, and because 
Portland cement will soon be made here in sufficient quantities to meet the 
entire home demand, and at prices so low that there will probably be little 
demand for this kind of dilution. 

409. Variation of Strength of Cement-mortar with Increasing Propor¬ 
tions of Sand. —This Jaw is largely a function of the methods employed in 
mixing the mortar and in compacting it in the moulds. When this is 



























































580 


THE MATERIALS OF CONSTRUCTION. 



Fig. 506. —Strength of “ Sand cement ” Mortar at Twenty-eight Days for Increasing; 
Proportions of Free Sand when mixed with “ Sand-cement ” containing 1 C.: 3 S.. 
(2 honindustrie-Zeitung, January 6, 1896.) 



Fig. 507.—Strength of Sand-cement Mortar with Varying Proportions of Sand. ( Thon * 

industrie-Zeitung, January 6, 1896.) 



































































TESTS ON CEMENTS , CEMENT-MORTARS, AND CONCRETES. 581 


thoroughly done, the strength of mortar composed of 1 C. : 1 S. will be 
found to be about as strong as, and often stronger than, that of the neat. 



Fig. 508. —Variation in Strength of “ Sand-cement ” Mortar when the Total Proportion 
of Sand is constant, but a Varying Proportion of Ground and Unground. ( Thon- 
industrie-Zeitung, January 6, 1896 ) 



Fig. 509. —Showing Reduction of Strength of Portland-cement Mortar, Six Months 
Old, with Increasing Proportions of Sand. (Wheeler, Rep. Chf. Engrs. 1895, p. 2982.) 


cement. Thus in Fig. 517 the 1 : 1 mortar was stronger than the neat 
Portland cement. The standard mixture of 3 S. : 1 C. snould have, in 
















































-582 


THE MATERIALS OF CONSTRUCTION. 


general, about one half the strength of the neat cement when six months 
old. It also appears from Figs. 509 and 511 that Portland-cement mortar 



Fig. 510.—Showing Reduction in Strength of Portland-cement Mortars, Six Months Old, 
with Increasing Proportions of Sand. (Wheeler, Rep. CZif. Eiigrs. 1895, p. 2982.) 

of 4 S. : 1 C. has the same strength at six months as natural-cement mortar 
of 2 S. : 1 C. of same age. 

Similar relations appear in Figs. 489, 494, 512, 513, and 515. 



Fig. 511. —Showing Reduction of Strength of Natural-cement Mortar, Six Months Old, 
for Increasing Proportions of Sand. (Wheeler, Rep. Chf. Engrs. 1895, p. 2982.) 

410. Variation of the Strength of Cement-mortars with a Variation in 
Size of the Sand-grains. —Photographs of sand-grains, natural size, obtained 

















































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 583 


by the use of graded sieves, are shown in Figs. 518 to 523. The effect of 
the variation in size of the sand-grains was discussed and results shown in 



Fig. 512.—Strength of Cement-mortars, at Six Months Old, for Varying Proportions of 

Sand. {Boston Main Drainage , 1885, p. 122.) 



Fig. 513.—Tensile Strength of Portland-cement Mortar. (Baker, in Masonry Construc¬ 
tion, p. 90.) 

Art. 317. It there appeared that sand which passes a No. 20 and stops on 
a No. 30 sieve (20 and 30 meshes per linear inch) gave the strongest mortars. 
















































584 


THE MATERIALS OF CONSTRUCTION. 


It is shown in Fig. 516 that mortar from this grade of sand is from 25 to 50 
per cent stronger than mortar made from sand which had passed a No. 40' 
and stormed on a No. 80 sieve. 



Fig. 514.—Ratio of Strength of Mortar to Strength of Neat Cement for Different Pro¬ 
portions of Sand. {Rep. N Y. State Engr. 1894, p 336.) 


m 


i 

~wm 

70/6. 

-KV 

C /Vr 

7 \ 








A 




' 






X<; 
X> ^ 

b 

V 

Ap > 








j — u 

£-- 


o 


/ 2 3 4 <5 6 

t 

Fig. 515. —Tensile Strength of Rosendale (Natural) 
Cement Mortar. (Baker, in Masonry Construc¬ 
tion p. 90.) 



Fig. 516.—Effect of Size of Sand- 
grains on the Strength of Ce¬ 
ment-mortar, 3 S.: 1 C. (Wheeler, 
Rep. Chf. Engrs. 1895, p. 3013.) 





























































TESTS ON CEMENTS , CEMENT-MOUTARS, AND CONCRETES . 585 

M. Feret 1 * has for many years made a study of the effects of the 
granulometric ” composition of the sand on the various qualities of tho 



Fig. 517. —Time Tests ou Three Kinds of Portland Mortar with Different Sands. (R. R L 

Gazette, 1892.) 


resulting mortars. \ He experimented with two sands of the following 
granulometric compositions: 


Kind of Sand. 

Large Grains, 

2.0 mm. to 5.0 mm. 

Medium Grains, 
0.5 mm. to 2.0 mm. 

Fine Grains, 
passing 0.5 mm. 


52* 

48 * 

0 

TTS n o ^Trniivi 1 lfit. . . .... 

1* 

24* 

75* 





The granulometric composition was found by sifting through thin plates 
having circular holes of 5 mm., 2 mm., and 0.5 mm. respectively, with the 


* Chef du laboratoire des Pouts et Chaussees a Boulogne-sur-Mer, France, 
f See his papers in An. cl. Fonts et Chaussees for Mar. 1890, July 1892, Aug. 1890, 
and in Baumaterialenkunde , vol. i, No. 10. 



























































586 


TEE MATERIALS OF CONSTRUCTION. 



Fig. 518.— Granite, size 80-100. 


Fig. 519.—River-sand, size 120-110. 




Fig. 520.—River-sand, size 20-30. 


Fig. 521.—River sand, size 20-30. 



Fig. 522 —Granite, size 12-16, Fig. 523.—River-sand, size 12-16. 

Photographs of Sand-grains, Natural Size. (Cooper, in Jour. Frank. Inst., vol. cxl* 

1896.) 







































TESTS ON CEMENTS , CEMENT-MORTARS, AND CONCRETES. 587 


results as indicated by the table above. When all possible proportions of 
coarse and tine sand had been tried with a cement ingredient varying from 
10 to 30 per cent of the total, it was found that the strongest mortar for any 
given percentage of cement teas always found for a weight of coarse sandX 
equal to twice the combined weight of the fine sand and the cement. With 
this condition fixed, the strength and cost of all mortar mixtures fulfilling 
this condition are given in Fig. 524. 



Fig. 524. —M. Feret’s Maximum Strength Mixtures iu which the Coarse Sand (S.) is 
twice the Combined Weight of the Fine Sand (s.) aud the Cement (c.). (An. d. Ponts 
et Chaussees, Aug. 1896, p. 191.) 

411. Relative Economy of Coarse and Fine Sand in Cement-mortars.— 

When the choice lies between a coarse sand and a fine sand exclusively for 
use in cement-mortar for any purpose, the preference should always be given 
to the coarse sand, even though its cost is many times that of the fine sand. 
Thus M. Feret gives as a generalization from his years of experimentation 
on this subject* a table from which Fig. 525 has been constructed. Here 
we have as a common argument the compressive strength of the mortar mix¬ 
tures, at the age of three months, for any given brand of Portland cement. 
In this figure we have for the two sands whose granulometric composition is 
given in the note below the figure: 

1. Weight of cement to use with one cubic yard of coarse sand to produce 
a mortar of any given strength. 

2. The same for fine sand. 

3. Weight of cement to use to produce one cubic yard of mortar of any 
given strength when coarse sand is used. 


* Iu Les Materiaux de Constructions (Baumaterialenkunde), vol. i. p. 139. 


































588 


THE MATERIALS OF CONSTRUCTION. 












































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 589 


4. The same when fine sand is used. 

5. Cost per cubic yard of coarse-sand mortars of any given strength. 

G. The same for fine-sand mortars when the fine sand costs only fifteen 
per cent as much as the coarse sand. 

i. The ratio of the volume of coarse sand to the volume of the mortar of 
any given strength. 

8. The same when fine sand is used. 

From these diagrams the following remarkable conclusions may be drawn: 

A. It requires about twice as much cement mixed with a given quantity 
of sand to produce a mortar of given strength when fine sand is used as it 
does with coarse sand 

B. The weight of cement per cubic yard of mortar of a given strength is 
about twice as much for fine sand as for coarse sand, with the ordinary mix¬ 
tures. 

C. The cost p)er cubic yard of coarse-sand mortar of a given strength 
(such as is found for the ordinary ratio 1 C. : 3 S.) is only about seventy-five 
per cent of the cost of a fine-sand mortar of the same strength, even when the 
coarse sa nd costs six and one-half t imes as much as the fine sand (coarse 
sand $1.30, and the fine sand $0.20 per cubic yard). 

412. Experiments with Sands of Artificial Granulometric Composition. 
—Very coarse or gravelly sands, containing pebbles as large as one-fourth 
inch in greatest dimension, may be introduced into a mortar used in making 
concrete, or in rough masonry, with great economic advantage. M. Feret 
has studied the effects of the use of such sands, mixed in various proportions 
with finer grades, and some of his results are given in Figs. 526 to 531 lie 
used fo v these experiments three grades of sand, namely: 


Grade of Sand. 

Passes a Perforated Plate 
having Holes of a Diameter of 

Is Stopped on a Plate having 
Holes of a Diameter of 

sjinrl. 

5 mm. or 0.2 in. 

2 mm. or 0.08 in. 

0.5 mm. or 0.02 in 

2 mm. or 0.08 in. 

0.5 mm. or 0.02 in. 

Medium sand. 

T^irw* sanrl . 




He made all possible mixtures of these three grades, representing each 
mixture by its position in an equilateral triangle, just as has been done in 
the case of the bronzes in Fig. 76. Thus in Fig. 526 let each apex of the 
triangle represent 100 per cent of one kind of sand, and on perpendiculars 
drawn from these points to the opposite sides let percentages be marked, 
reducing to zero on those sides as shown in the figure, and let lines be drawn 
through these points parallel to the several sides as shown. Then may any 
particular composition of sand, made up of any given proportions of the 
three grades, be represented by the position of a point which shall be distant 
from the several sides by amounts equal to the three percentages, as indi¬ 
cated on the normals to these sides. This follows from the geometrical 















-590 


THE MATERIALS OF CONSTRUCTION. 



Fig. 526 —Showing the Method of Representing 
Proportionate Mixtures of Three Ingredients. 
G = coarse sand, 0.2 in. to 0.08 in. in diameter. 
M = medium sand, 0 08 in. to 0.02 in. in diameter. 
F = fine sand less than 0.02 in. in diameter. 


Fig. 527.— Compressive Resistance of Portland- 
cement Mortars, in pounds per square inch, after 
nine months in air and then three months in 
sea-water. Mortar 1 C. : 3 S. in all cases, but 
the composition of the sand varying according 
to position in the triangle. 



Fig. 528 —Compressive Resistance of Portland- 
cement Mortars, 1 C. : 3 S , in pounds per square 
inch, after one year in sea-ioater. Shaded 
part indicates mixtures which were partially 
disintegrated. 


Fig. 529 —Compressive Resistance of Portland 
cement Mortars, 1 C. : 3 S., in pounds per square 
inch, after one year in fresh water. 



Fig. 530.—Actual Solid Contents (C. -f- S.) of Port- 
land-cement Mortars, 1 C.: 3 S , in terms of the 
total bulk of the mortar. 


Fig. 531. — The Porosity of Portland cement 
Mortars, 1 C. : 3 S., as indicated by the percent¬ 
age of water absorbed by the mortar after it 
had hardened and dried. 


Samples of M. Feret’s Diagrams illustrating Effects of Varying the Granulometric 
Composition of the Sand used in making Portland-cement Mortars. The actual sizes 
of the Sand-grains of the Three Ingredients are indicated by the small circles at 

file corners nf the Prion rrlpq (An tl T>nnU et nh,t*,Q 0 af , 0 >7 ^..l — /-i cu\n\ 





























TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 591 


proposition that the sum of the three normals from any point in an equh 
lateral triangle to the three sides is equal to the common altitude of the 
triangle. The various characteristics of such mortars may now be repre¬ 
sented by lines drawn upon these triangles, which shall join points of equal 
numerical value in the quality under consideration, the same as contour-lines 
on a map join points of equal elevation above a given datum plane. 

11ms in Fig. 527 the compressive resistance in pounds per square inch 
is indicated for all possible mixtures of these three grades of sand, there 
being in all cases a total of 3 S. to 1 C. by weight. These samples were all 
left nine months in the air and then three months in sea-water. From this 
figure we conclude: 

A. That a sand composed of 4 parts of very coarse sand (0.08-0.20 in. 
diam.) to 1 part of very fine sand (less than 0.02 in. diam.) makes the 
strongest possible mortar of 1 C. : 3 S. 

B. That the strength of such a mortar is more than twice as much as 
the same mortar 1 C. : 3 S. when the sand is composed of what is 
commonly regarded as “coarse sand ” (0.02-0.08 in. diam.), and more than 
three times as strong as the same (1 C. : 3 S.) mortar when the sand is very 
fine (less than 0.02 in. diam.). 

0. That a mixture of two grades of sand of widely different sizes gives a 
great deal stronger mortar for given proportions of sand and cement than 
does any particular size w T hen used by itself. 

D. It follows from the above that it is well to employ as coarse a sand 
as the work will admit of, even to the finer gravels in the case of coarse 
masonry, and especially with the concretes. 

E. It follows also that in the case of concrete mixtures it is well to leave 
in the smaller sizes of the crushed rock, provided the very fine particles be 
excluded. This has been found to be the case in actual practice. 

F. That it would pay to use very coarse sand at a very much higher price 
than to use medium or fine sand at a low price, or even if its cost be nil. 

Very similar results to the above are shown in Figs. 528 and 529, from 
which like conclusions may be drawn. The shaded part of Fig. 528 indicates 
that for these mixtures, after exposure to sea-water for one year, there were 
some signs of disintegration, due doubtless to the greater permeability of 
these mixtures. (A distinction must be drawn between permeability and 
poro.sity. See next article.) 

413. The Porosity of Mortars as affected by the Size of the Sand-grains. 

—Figs. 530 and 531 indicate the relative and absolute porosity of various 
sand mixtures as affected by the granulometric composition of the sand used. 
Thus Fig. 530 gives the actual solid contents, per unit volume of mortar, of 
the cement and sand combined which entered into the composition. Fig. 
531 gives the volume of water absorbed, per unit volume of the dry mortar, 
for all granulometric compositions of the sand. In both cases the greatest 
porosity is found with the finer grades of sand, and the least for a mixture of 
two of very coarse (gravelly) sand to one of fine sand. 


592 


THE MATERIALS OF CONSTRUCTION. 


The relative permeability cannot be assumed to vary with the porosity, 
since a given degree of porosity with coarse sand produces a much more 
permeable mortar than the same degree of porosity with fine sand. Hence 



in Fig. 528 the disintegrating effect of the sea-water was manifested with the 
coarse-sand mixtures, while the fine-sand mixtures did not reveal any such, 
action, although its porosity was much greater. 




















































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 593 

414. The Effect of Long Storage on the Strength of Cement.—The effect 
-of long storage is to reduce the strength of the cement more or less, whether 
this he Portland, natural, or slag cement. The injury, however, is not as 
great as is commonly supposed. Thus in Fig. 532 we have both tensile 
and compressive tests on standard Portland-cement mortar, 1 C. : 3 S., for 
various conditions from “fresh burnt” to “very lumpy.” The loss of 
tensile strength seems to be less than the loss of compressive strength, 
though, except in the latter case for the “ very lumpy,” the loss is not 
material. 

In the case of natural cement over thirty days old the loss of tensile 
strength is considerable, as shown in Fig. 533. Here, however, the cement 
Fad been spread out and exposed to the air. 



Fig. 533.—Effect of Aeration on the Strength of Natural-cement Mortar. (Wheeler, 

Rep. Chf. Engrs. 1895, p. 2962.) 

In both the natural and in the slag cements there is free lime, which 
•changes to the inert carbonate of lime when exposed to air containing carbon- 
dioxide gas. The result is to destroy this lime ingredient. In other cases, 
where there is unslacked free lime, a long aeration allows this ingredient 
to slack, and so prevents this action in the hardened cement, which would 
swell and crack it. It is the object of the boiling test to detect the presence 
of any such slow-slacking free lime in the cement. The effects of long 
storage of slag-cement containing various proportions of free lime on both 
the tensile and the compressive strength are shown in Fig. 534. 

415. Effect of Regauging after Set Begins.—It is commonly understood 
that cement which has begun to set is more or less weakened by regauging, 






















594 


THE MATERIALS OF CONSTRUCTION. 


and that such cement should never be used in practice. The results shown 
in Figs. 535, 536, and 537 reveal to what extent the mortar is weakened. 
Thus from Fig. 535 it may be seen that a quick-setting natural cement 



mixed neat loses ove r 25 per cent of its strength at six months from having 
been regauged once one hour after wetting. When regauged repeatedly in 
3 or 5 hours it 1r ^es 40 per cent of its normal strength. 






























































































































TESTS ON CEMENTS, CEMENT MORTARS, AND CONCRETES. 595 


From Fig. 536 it appears that a Louisville-cement mortar 1 C. : 2 S. 
loses 40 per cent of its normal strength at three months by standing 20 
minutes after wetting before moulding, and 80 per cent of its normal 



Fig. 535,— Effect of Regauging a Quick-setting, Neat Natural-cement Mortar, 

Six Months. (Rep. n lif. Engrs. 1895, p. 2980.) 


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Fig. 536.—Effect on the Strength 
of Louisville-cement Mortar of 
allowing it to stand a given 
time before putting into the 
moulds. (Jour. 1 Vest. Soc. 
Engrs., vol. i. p. 82.) 



Fig. 537. —Strength of Regauged Neat Port¬ 
land Cement after Six Months’ Harden¬ 
ing in Water. Time of setting: begins 
in 50 min., ends in 3 hrs. 25 min. 
(Wheeler, Rep. Chf. Engrs. 1895, p. 
2979.) 

































































1596 


THE MATERIALS OF CONSTRUCTION 


strength by standing one hour before moulding. The loss of strength in the 
1 C. : 1 S. mortar, though serious, is not so great. This is, however, a very 



quick-setting cement, and one which should evidently be used inside of 20 
minutes from the instant of wetting it. 

The loss of strength from regauging one or more times a neat Portland- 
cement mortar, during a period of from one to six hours, is shown in Fig. 
















































































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 597 


537. This cement completes its set in 3 hours 25 minutes, and loses 18 
per cent from being regauged once in five hours or three dimes in three 
]lours. Evidently any cement will be greatly weakened if used after it has 
set. 

416. Effect of Carbonic-acid Gas on the Hardening of Natural- and Slag- 
Cement Mortars. —These two classes of cement have more or less free lime 
in their composition, and the action of the C0 2 on this is to change it into 
the carbonate, CaC0 3 (limestone), which would naturally add to the strength 
of the mortar. As Portland cement does not contain free lime to any 
appreciable extent, it would not be similarly affected. In Fig. 538 the 
effect of C0 2 on a natural-cement mortar, 1C. : 3 S., is shown to be very 
great on both the tensile and the compressive strength. 

From Fig. 539 the effect on slag-cement is not so great, although quite 
marked. It may further be observed from this dragram that while harden¬ 
ing in perfectly dry air is very favorable to the natural cement, it is very 
unfavorable to the strength of the slag-cement. This would also be found 
to be the case with Portland-cement mortar. Why hardening in moist air 
at 120° F. (50° C.), which is rich in C0 2 , should be so very unfavorable to 
the strength of natural cement does not appear. 


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Fig. 540.—Adhesive Strength of Portland-cement Mortar, 1 C. : 1 S., Twenty-eight 
Days Old, to Different Substances, and the Cohesive Strength of the Mortar it¬ 
self. (Wheeler, Rep. Chf. Engrs. 1895, p. 3019.) 


417. The Adhesive Strength of Cement-mortars. —This is a subject of 
very great importance, but one which has not been commonly investigated. 
It is to be hoped that the standard methods proposed for this test by the 
French Commission will lead to further experiments giving comparable re¬ 
sults. 



























598 


THE MATERIALS OF CONSTRUCTION. 


In Fig. 540 the adhesive strength of Portland-cement mortar, 1 C. : 1 S., 
is given for various substances. Here small disks of the substance, 1 inch 
square and £ inch thick, were prepared and inserted transversely at the centre 
of the briquette-mould, and the briquette pulled in the usual manner, with 
the results as shown. It thus appears that, whereas the cohesive strength 
of this mortar was 710 lbs., its adhesive strength varied from 300 lbs. on 
sawn brick to 85 lbs. per square inch on sandstone having a cleavage surface. 

In Fig. 541 it is shown that while Portland-cement mortar will adhere 


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NEAT IC: IS NEAT |C:IS 

fresh FRESH 7 DAYS OLD 7 DAYS OLD 

LOUISVILLE CEMENT 

Fig. 541.—Adhesion between Louisville (Natural) and Portland Cement Mortars. {Jour. 

West. Soc. Engrs., vol. i. p. 82.) 

to natural (Louisville) cement mortar when both are fresh, it will scarcely 
adhere at all to a neat natural-cement surface after it is seven days old, and 
it adheres very poorly to a 1 C. : 1 S. natural-cement mortar a week old. 
The neat Poitland cement did adhere to the neat Louisville cement one 
week old with a force of 85 lbs. per square inch, but the Portland-cement 
sand-mixtures would not adhere to it with any appreciable force. 

I lie adhesion of natural and Portland cement mortars to sawn limestone, 
as compared with their cohesive strength, is shown by the diagrams in Fig’ 





















TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 599 



Fig. 542.—Relation between the Adhesive Strength at Twenty-eight Days of Cement- 
mortars to Sawn Limestone and the Cohesive Strength of the Mortars themselves, 
(Wheeler, Rep. Chf. Engrs. 1895. pp. 3020-21.) 



Fig. 543.—Adhesive Strength of Mortar to Brick Surfaces. ( Baker's Masonry, p. 94.) 
























































600 


THE MATERIALS OF CONSTRUCTION* 









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Fig. 544a.—Showing the Variation in 
the Modulus of Elasticity of Port¬ 
land-cement Mortar in Compres¬ 
sion, at the age of Three Mouths 
when tested in Cylinders 10 in. in 
Diameter and 40 in. long. (Prof. 
C. Bach in Zeits Ver . Denis . Trig ., 
Nov. 28, 1890. 


Fig. 544.—Relation between the Cohesive Strength of Cement-mortar and its Adhesive 
Strength to Brick Surfaces when Two Bricks are cemented together in cruciform 
shape and pulled normally. The results are the means of three months’ and six 
months’ tests on both die and stock brick. (Wheeler, Rep. Chf. Engrs . 1895, p. 
3022-4.) 



Fig. 545.—Adhesion of Plain 1-incli Round Bolts in Neat Portland-cement Mortar, Age 
One Month. Adhesion given in pounds per square inch of surface of bolt em¬ 
bedded. (Wheeler, Rep. Chf. Engrs. 1895, p. 2941.) 



























































TESTS ON CEMENTS , CEMENT-MORTARS , 4AD CONCRETES . €01 


54'^. In general we may say the adhesive strength here shown is less than 
one half the cohesive strength. 

The adhesive force of ordinary cement-mortars to brick surfaces is very 
small, as shown by Figs. 543 and 544. A strength of 25 lbs. per square inch 
seems to be about all that can be ordinarily counted on This low adhesive- 
strength may be partly due to the fact that the bricks are covered with a. 
coating of disturbed and loose particles. A clean, fresh fracture would 
probably show a much greater cohesion. 



The adhesion of cement-mortar to anchor-bolts embedded in stone is very 
great, as shown by Fig. 545. These tests agree well with experiments made 
bv the author. The ultimate strength at three or six months would b& 












































602 


THE MATERIALS OF CONSTRUCTION * 


nearly twice as much as shown in the diagrams, which are for an age of four 
weeks* The same department obtained about twice the adhesive strength 
shown in Fig. 545 by using limestone screenings, passing a f-inch-mesh sieve, 



using 2 S. to 1C. Hence the ultimate adhesive strength of a good Portland 
cement with limestone screenings, 1 0. : 2 S., to plain iron or steel bolts, 
may be taken at about 1000 lbs. per square inch. To develop a working 
strength on anchor-bolts, therefore, of 20,000 lbs. per square inch would re- 






























































TESTS ON CEMENTS , CEMENT-MORTARS, AND CONCRETES. G03 


quire a depth of adhesive surface equal to 20 diameters of the holt. To pro¬ 
vide a sufficient factor of safety a depth of 30 or 40 diameters should ho. 
used. 

418. Compressive Strength and Elasticity of Cement and Concrete.—In 

Fig. 540 are shown the results of Prof. Bach’s tests on concrete columns 10 



inches in diameter and 40 inches long. The deformations of these blocks 
were obtained with the apparatus shown in Fig. 201, p. 350. These blocks 
were composed of Portland cement, sand, and gravel, and they exhibit two- 
remarkable characteristics. They do not give the reverse-curved stress- 







































































604 


1IIE MATERIALS OF CONSTRUCTION. 


diagrams commonly obtained with concrete and stone blocks and shown in 
Figs. 547 and 548, and they also give very high moduli of elasticity. The 



Fig 549.—Showing Method of Failure of Cement Cubes. ( Wat. Ars. Rep. 1884.) 
author has not found any other tests giving these two characteristics in so 
marked a degree. The mixtures were doubtless very carefully made. 






TESTS ON CEMENTS , CEMENT- MORTARS, AND CONCRETES. 605 


Figs. 547 and 548 are compiled from Gilmore’s Limes , Mortars , 
Cements. Here the modulus of elasticity is only from one third to one half 
that obtained by Bach,* and there is always a large permanent set under the 
earliest, or smallest, loads. Probably this is due to imperfect mixing or to 
poor compacting in the moulds, or to both. Gilmore’s tests were made on 
the Emery machine at the Watertown Arsenal. The manner in which these 
cubes fail under compression is shown in Fig. 549. Bach’s moduli of 
elasticity on cement-mortar columns are given in Fig. 544 a, p. 600. 

419. Strength and Economy of Cement-mortar and Concrete. —There is 
no very uniform practice in America in the number of parts of sand to one 
of cement to be used in mortars. In general natural cement is used with 
one or two parts of sand, while Portland cement is commonly used with three 
parts of sand to one of the cement by measure. Whether the cement is to 
be measured in the original packages or in the loose condition it assumes 
when turned out is a matter of great significance, but no uniform practice 
is followed, and usually the specification is defective in not defining which 
method is to be employed. The amount of sand which may be used with a 
given cement depends on the percentage of voids in the sand, and on the 
fineness of the cement. If the sand-grains are graded in size, the voids are a 
smaller proportion; and if the cement is all finely ground, it is all active. 
Such parts of the cement as will not pass a No. 200 sieve (40,000 meshes per 
square inch) has no value as a cement and acts as so much sand. 

In Fig. 550 are shown the results of an excellent series of tests made by 
Mr. E. S. Wheeler, M. Am. Soc. C. E., in connection with the building of 
the St. Mary’s Falls Canal lock. Here the natural-cement mortars all give 
the greatest strength for a given cost, the price of the natural cement being 
43 per cent of that of the Portland cement, delivered on the works. The 
most economical natural-cement mortar is that of 1 C. . 2 S. oi 1 0. . 3 S. 
Probably 1 C. : 2| S. is the best mixture for natural cement. With the 
Portland cement the mixtures 1 C. : 2 S., 1 C. : 3 S., and 1 C. : 4 S. were 
all about equally strong for a given cost, or, what is the same thing, these 
mixtures are about equally expensive for a given strength. 

Evidently an ideal concrete is one in which all voids are filled, all sand- 
grains are coated with cement, and all pebbles, gravel, or broken stones are 
coated with mortar, with no excess of cement or mortar. This requires that 
enough cement must be used to fill the voids in the sand (plus some excess 
to cover imperfect mixing), and enough mortar used to fill the voids in the 
stone or gravel (plus an excess as before). In the Report of the Chief of 
Engineers of the U. S. Army for 1895 ,\ pp. 2924 t o 2 931, will be fou nd 

HApo reatUhe^nodulus of elasticity from any of the curves in Figs. 546, 547, or 548, 
find the change of load per square inch for which the proportionate compression is 
0.001, and multiply such change in load by 1000, using the straight portion of the 
diagrams for such readings. 

f Under the direction of Mr. E. S. Wheeler. U. S. Ass’t Eng’r in charge of the con¬ 
struction of locks on the St. Mary’s Falls Canal. 






606 


THE MATERIALS OF CONSTRUCTION . 


the records of the most complete series of tests of the cross-breaking strength 
of concrete beams ever made. These beams were all 10 inches square, and 
were broken on a span of 4 feet. There are here recorded the results of 
tests on over one hundred such beams, forty of which were again broken on 
a span of 20 inches. The first breaks were at one year old, and the second 
at 22 months. All kinds of mixtures and conditions were used in the making 
of the beams, and they were covered by moist earth during the entire harden¬ 
ing period, or until broken.* In all these tests the proportions by both 



Fig. 550.—Relation between Strength and Cost of Natural- and Portland-cement 
Mortars. Prices : Nat. cem. = $1.30 per bbl.; Port. cem. = $3.00 per bbl.; sand = 
$1.00 per cu. yd. (Wheeler, Rep. Chf. Engrs. 1893, vol. iv. p. 3022.) 


weight and by volume are recorded, and the cost of each part, and many 
other pertinent facts. A few of these results, which were of the nature of a 
series, are plotted in Figures 551 to 554, and the full record of the tests is 
given in Table XXXVII. 

In Fig. 551 the cost per cubic yard and the cross-breaking strength in 
pounds per square inch are given for various mixtures of Portland-cement 
concrete. From this diagram the most economical mixture does not appear. 
Evidently the greatest economy corresponds to the greatest ratio of strength 
to cost, or, what is the same thing, the minimum ratio of cost to strength. 
This may be shown by plotting one of these ratios to the number of parts of 
sand and stone to one of cement. This is done in Fig. 552. From this it 
appears that the most economical mixture of Portland-cement concrete (the 

* The series was not completed at the time of the 1895 report, and the 1896 report 
will contain further results. 



































TESTS ON CEMENTS, CEMENT- MO It TA US, AND CONCRETES. 607 


prices being $3.00 per barrel for cement, 50 cents per cubic yard of sand, 
and $1.00 per cubic yard of stone or gravel) is 1 C. : 3 S. : 7£ broken stone 
or gravel, all by volume.* The cross-breaking modulus of rupture of this 



800 400* MO 


Fig. 551. —Relation between Cost and Strength of Portland-concrete Beams Nineteen 
Months Old. Each result is the mean of two tests on beams 10 iu. square. Por¬ 
tions of sand and stone are given to 1 of cement. Cement $3.00 per bbl.; sand 
$0.50 and stone $1.00 per cu. yd. (Wheeler, Rep. Chf. Engrs. 1895.) 

mixture (the value of / in the formula M — }fbh\ where M — bending 
moment, b = breadth, and h = depth of the beam) is about 500 lbs. per 
square inch at the age of 19 months. A mixture of 1 C. : 2 S. : 5 stone is 


* The cement is here taken as packed in the barrel, and the sand aud stone are taken 
loose. The dry weights of each are also given in the original tables. 




































TABLE XXXVII.—COMPOSITION, COST, AND STRENGTH OF PORTLAND-CEMENT-CONCRETE BEAMS 10 INCHES SQUARE 
MADE AND TESTED IN CONNECTION WITH THE CONSTRUCTION OF THE ST. MARY S CANAL LOCKS. 

(Rep.Chf. Engrs. TJ. S. A., 1895 , Appendix LL, p. 2924 . 


608 


TEE MATERIALS OE CONSTRUCTION. 


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TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 609 


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610 


THE MATERIALS OF CONSTRUCTION, 


TABLE XXXVIIrt.—COMPOSITION, COST, AND STRENGTH OF NATURAL-CEMENT- 
CONCRETE BEAMS 10 INCHES SQUARE (ST. MARY’S CANAL LOCKS). 


Proportionate 
Amounts for 
1 Cubic Foot of 
Packed Cement 
(75 lbs. Natural, 
104 lbs. Portland) 


Proportionate 
Amounts for 
1 bbl. Packed 
Cement (280 lbs. 
Natural. 380 lbs. 
Portland). 


Cost 

per 

Cubic 

Yard. 


Transverse 
Strength on 
4-foot Span. 


Sand, Loose, Dry. (Cubic Feet.) 

Stone, Loose. (Cubic Feet A 

i 

Mortar, Made. (Cubic Feet.) 

Rammed .Concrete, Made. 

(Cubic Feet.) 

Sand, Loose, Dry. (Cubic Feet) 

Stone, Loose. (Cubic Feet.) 

, 1 

Mortar, Made. (Cubic Feet.) 

Rammed Concrete, Made. 

(Cubic Feet.) 

Mortar. 

Concrete. 

Age when Broken. 

1.78 

4.18 



6.7 

15.6 





1 yr 

1.7s 

4.18 



0.7 

15.6 





1 yr 

.1.78 

4.18 



6.7 

15.6 

9.1 


4.14 


1 yr 

'2.16 

4.18 



8 1 

15.6 

9.9 


4.00 


1 yr 

2.16 

4.18 



8.1 

15.6 





1 yr 

2. 10 

4.18 



8.1 

15.6 





1 yr 

2 30 

8 23 

2.83 8.44 

8.57 

3.07 

10.6 

31 5 

3.62 

2.25 

1 yr 

2 27 

6.86 

2.71 

7.18 

8.47i2 56 

10.1 

26.9 

3.89 

2.45 

1 yr 

2.25 

10.17 

2.72 9.92 

8.42 

3 80 

10.2 

37.1 

3.89 

2.10 

1 yr 

2.27 

6.86 

2.71 

6.86 

8.47 

2.56 

10.1 

25.6 

3.96 

2.55 

1 yr| 

2 2o 

10.17 

2 72 

9 12 

8.42 

3.80 

10.2 

34.1 

4 24 

2.30 

1 yr 

1.87 

5 33 

2 42 

5.55 

7.00 

20.0 

9.1 

20.8 

4.24 

2.80 

1 yr 

1.87 

5.33 

2.42 5.55 

7.00 

20 0 

9.1 

20.8 

4.24 

2.80 

1 yr 

1.87 

5 33 

2.42 5.55 

7.00 

20.0 

9 1 

20 8 

4.24 

2.80 

1 yr 

1.50 

5.38 

2.07 

5.42 

5.6 

20.2 

r* n 

i . i 

20.3 

4.88 

2.85 

1 yr 

1.50 

5.38 

2.07 

5 42 

5.6 

20 2 

7.7 

20 3 

4.88 

2.85 

1 yr 

1.50 

5.38 

2.07 

5 42 

5.6 

20.2 

r- rv 

i . i 

20 3 

4 88 

2 85 

1 y 

1.12 

4.15 

1.8(4.60 

4.2 

17.8 

6 7 

17.2 

5.50 

3.17 

1 yr 

1.12 

4.15 

1.80 

4.60 

4.2 

17.8 

6.7 

17.2 

5 50 

3.17 

lyr 

0.75 

3.05 

1.46 

3.17 

2.8 

11.4 

5 5 

11.9 

6 64 

4.05 

19m 

0.75 

3.05 

1.46 

3.17 

2 8 

11.4 

5.5 

11.6 

6.64 

4.05 

19m 

1.50 

4.06 

2 09 

4.37 

5.6 

15 2 

7.8 

16 4 

4.85 

3.20 

19m 

1.50 

4.06 

2 09 

4.37 

5 6 

15 2 

7.8 

16.4 

4.85 

3.20 

19m 

2.25 

5.90 

2.85 

6.00 

8.4 

22.1 

10 7 

22 5 

3.65 

2.70 

19m 

2 25 

5.90 

2.85 

6.00 

8.4 

22 1 

10 7 

22.5 

3 65 

2.70 

19m 

3 00 

7.40 3.55 

7.60 

11.2 

27.7 

13.3 

28.5 

3.10 

2.40 

19m 

3.0.) 

7.40 3.55 

7.60 

11.2 

27.7 

13 3 

28.5 

3 10 

2 40 

19m 

2 25 

6.56 

2.85 

6 30 

8.4 

24.5 

10 7 

23 6 

3.63 

2.70 

11 m 

2.25 

0.56 

2.85 

6.30 

8.4 

24.5 

10.7 

23.6 

3.63 

2.70 

11m 

2 28 

6.56 

2 85 

6.56 

8.5 

24.5 

10 7 

24 6 

3 63 

2 60 

11m 

2 28 

6.56 

2 85 

6 56 

8 5 

’•24 . 5 

10.7 

24.6 

3.63 

2 60 

11m 

2 2f 

6.56 


6 73 

8 4 

24.5 


25 2 


2.50 

11m 

2 25 

6.56 


6 73 

8 4 

24.5 


25 2 


2.50 

11ml 

1 29 

7.30 

2 02 

6.82 

4.83 

27 3 

7.56 

25.6 

5 00 

2.55 

11m 

1.29 

7.30 

2.02 

6 82 

4.83 

27.3 

7.56 

25 6 

5.00 

2.55 

11m 

2 28 

6 56 2 89 

6.82 

8.5 

24 5 

10 85 

25.6 

3.57 

2 50 

11m 

2.28 

6.56 

2.89 

6.82 

8 5 

24.5 

10.85 

25 6 

3.57 

2.50 

11m 

2 28 

6 56 

2 85 

7 13 

8 5 

24.5 

10 7 

26 7 

3 63 

2.35 

11m 

2.28 

6 56 

2.85 

7.13 

8.5 

24.5 

10 7 

26.7 

3 63 

2 35 

11m 

2 28 

6.56 

2.85 

6 82 

8 5 

24.5 

10 7 

25 6 

3.63 

2.50 

11m 


"t 


o' 
GO 
£ u 
- <D 

= -ft 


3 £> 

03 


o 

X ft 


5 ^ 


136 124 

148 150 


140 

140 

141 

139 

150 

151 
146 
146 
131 

138 

139 
138 

140 

136 

140 

137 


222 

94 

96 

202 

120 

74 

110 

123 

74 

181 

214 

175 

194 

210 

275 

306 

363 


313 

351 

206 

274 

187 

185 

237 

229 


1 11 
216 


216 

173 

230 

225 

187 

216 


101 

144 

130 


Trans¬ 
verse 
Strength 
on 20-inch 
Span. 


a; 

be 

< 


O' 

m 

<D u 
u 0) 

5 a 

3 33 

Pi j 


X g 
3 n 


T3 u 
3 'K 


Remarks. 


35m 

22m 

22m 

22m 

22m 

22m 

18m 

18m 

18m 

18m 

18m 

18m 

18m 


337 

187 

197 

197 

253 

151 

276 

246 

287 

261 

256 


312 

422 


Sandstone f" to 3" in size 
Limestone, (D. I.), in to 
3" in size 

Limestone (K.I.),“shavings” 
j being flat spalls 
jSaudstone 
Limestone (D. I.) 

Limestone (K.I.),“shavings” 
or flat spalls 
Gravel to 1" in size 

ii it 

ii it 

Sandstone, f" to 3" in size 

ti u 

“ quite dry 

it ii ii 

<i ii ii 

1 

! Sandstone, f" to 3" in size, 
somewhat dry 

J 


I Sandstone, f" to 3" in size, 
f somewhat wet 


1 

[ Sandstone, f" to 3" in size, 
[ somewhat dry 


(Limestone (D. I.), no 

) screenings 

) Limestone (D. I.), 10 pts 

V screenings to 100 pis 

) stone 

] Limestone (D. I.), 17 pts. 

screenings to 100 pts. 
j stone 

j Limestone (D. I), 50 pts. 

V screenings to 100 pts. 

) stone 

) Limestone (D. I.), 100 pts. 
> screenings to 100 pts. 

) stone 

Limestone (D I.), s v reen- 

ings only 
















































































TESTS ON CEMENTS, CEMENT-MORTARS, ANT) CONCRETES. 610 a 

TABLE XXXVII^.— PROPORTIONS OF MATERIALS IN CEMENT CONCRETE, 

MODERATELY RAMMED. 

(From actual experiments made by Edwin Thatcher, M. Am. Soc. C. E.) 


Concrete with Stone 1 Inch and Under. 

Proportions of Mixture. 

Required for 1 Cubic 
Yard. 




® is 

i? 


. 

0,2 

V 


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.2 2 o 

<D i- 

'z 

o3.o t- 

s 

ci 

o 

5“ a 

jffl 


c ~ ^ 

o 

CO 

oa 

« 

o 

CO 

cc 

1 

1 

2.0 

1.42 

2.57 

0.39 

0.78 

1 

1 

2.5 

1.79 

2.29 

0.35 

0.70 

1 

1 

3.0 

2.14 

2.06 

0.31 

0.94 

1 

1 

3.5 

2.50 

1.84 

0.28 

0.98 

1 

1.5 

2.5 

1.40 

2.05 

0.47 

0.78 

1 

1.5 

3.0 

1.68 

1.85 

0.4'! 

0.84 

1 

1.5 

3.5 

1.97 

1.72 

0.39 

0.91 

1 

1.5 

4 0 

2.25 

1.57 

0.36 

0.96 

1 

1.5 

4.5 

2.53 

1.43 

0.33 

0.98 

1 

2.0 

3.0 

1.38 

1.70 

0.52 

0.77 

1 

2.0 

3.5 

1.61 

1.57 

0.48 

0.83 

1 

2.0 

4.0 

1.84 

1 46 

0.44 

0.89 

1 

2.0 

4.5 

2.07 

1.36 

0.42 

0.93 

1 

2.0 

5.0 

2.31 

1.27 

0.39 

0.97 

1 

2.5 

3.5 

1.37 

1.45 

0.55 

0.77 

1 

2.5 

4.0 

1.57 

1.35 

0.52 

0.82 

1 

2.5 

4.5 

1.76 

1.27 

0.48 

0.87 

1 

2.5 

5.0 

1.96 

1.19 

0.46 

0.91 

1 

2.5 

5.5 

2.16 

1 .13 

0 43 

0.94 

1 

2 5 

6.0 

2.36 

1.07 

0.41 

0.97 

1 

3.0 

4.0 

1.34 

1.26 

0.58 

0.77 

1 

3 0 

4.5 

1.51 

1.18 

0.54 

0.81 

1 

3.0 

5.0 

1.68 

1.11 

0.51 

0.85 

1 

3.0 

5.5 

1.85 

1.06 

0.48 

0.89 

1 

3.0 

6.0 

2.02 

1.00 

0.40 

0.92 

1 

3.0 

6.5 

2.18 

0.96 

0.44 

0.95 

1 

3.0 

7.0 

2.35 

0.91 

0.42 

0.97 

1 

3.5 

5.0 

1.48 

1.05 

0.56 

0.80 

1 

3.5 

5.5 

1.63 

1.00 

0.53 

0.84 

1 

3.5 

6.0 

1.77 

0.95 

0.50 

0.87 

I 

3.5 

6.5 

1.92 

0.92 

0.49 

0.91 

1 

3.5 

7.0 

2.06 

0.87 

0.47 

0.93 

1 

3.5 

7.5 

2.21 

0.84 

0.45 

0 96 

1 

3.5 

8.0 

2.36 

0.80 

0.42 

0.97 

1 

4.0 

6.0 

1.57 

0.90 

0.55 

0.82 

1 

4.0 

6.5 

1.70 

0.87 

0.53 

0.85 

1 

4.0 

7.0 

1.83 

0.83 

0.51 

0.89 

1 

4.0 

7.5 

1.96 

0.80 

0.49 

0.91 

1 

4.0 

8.0 

2.10 

0 77 

0.47 

0.93 

1 

4.0 

8.5 

2.23 

0.74 

0.45 

0.95 

1 

4.0 

9.0 

2.36 

0.71 

0.43 

0.97 

1 

5.0 

9.0 

1.94 

0.66 

0.50 

0.90 

1 

5.0 

10.0 

2.15 

0.62 

0.47 

0.95 

1 

6.0 

11 0 

2.04 

0.55 

0.51 

0.93 

1 

6.0 

12.0 

2.22 

0.52 

0.48 

0.95 

1 

7.0 

13.0 

2.07 

0.47 

0.50 

0.93 

1 

7.0 

14.0 

2.23 

0.45 

0.48 

0.96 



Concrete with Stone 2 

£ Inches aud Under. 

Proportions of Mixtui 

e. 

Required for 1 Cubic 
Yard. 

Cement. 

Sand. 

Stone. 

Ratio: 

Stone 

Mortar’ 

Cement. 

Barrels. 

Sand. 

Cubic 

Yards. 

Stone. 

Cubic 

Yards. 

1 

1 

2.0 

1.42 

2.63 

0.40 

0.80 

1 

1 

2.5 

1.79 

2.34 

0.36 

0.89 

1 

1 

3.0 

2.14 

2.10 

0.32 

0.96 

1 

1 

3.5 

2.50 

1.88 

0.29 

1.00 

1 

1.5 

2.5 

1.40 

2.09 

0.48 

0.80 

1 

1.5 

3.0 

1.68 

1.90 

0.43 

0.87 

1 

1.5 

3.5 

1.97 

1.74 

0.40 

0.93 

1 

1.5 

4.0 

2.25 

1.61 

0.37 

0.98 

1 

1.5 

4.5 

2.53 

1.46 

0.33 

1.00 

1 

2.0 

3.0 

1.38 

1.73 

0.53 

0.79 

1 

2.0 

3.5 

1.61 

1.61 

0.49 

0.85 

1 

2.0 

4.0 

1.84 

1.48 

0.45 

0.90 

1 

2.0 

4.5 

2.07 

1.38 

0.42 

0.95 

1 

2.0 

5.0 

2.31 

1.29 

0.39 

0.98 

1 

2.5 

3.5 

1.3 

7 

1.48 

0.56 

0 79 

1 

2.5 

4.0 

1.57 

1.38 

0.53 

0.84 

1 

2.5 

4.5 

1.7 

6 

1.29 

0.49 

0.S8 

1 

2.5 

5.0 

1.96 

1.21 

0.46 

0.92 

1 

2.5 

5.5 

2.16 

1.15 

0.44 

0.96 

1 

2.5 

6.0 

2.36 

1.07 

0.41 

0.98 

1 

3.0 

4.0 

1.34 

1.28 

0.58 

0.78 

1 

3.0 

4.5 

1.51 

1.20 

0.55 

0.82 

1 

3.0 

5.0 

1.68 

1.14 

0.52 

0.87 

1 

3.0 

5.5 

1.85 

1.07 

0.49 

0.90 

1 

3.0 

6.0 

2.02 

1.02 

0.47 

0.93 

1 

3.0 

6.5 

2.18 

0.98 

0.44 

0 96 

1 

3.0 

7.0 

2.3 

5 

0.92 

0.42 

0.98 

1 

3.5 

5.0 

1.48 

1.07 

0.57 

0 82 

1 

3.5 

5.5 

1.63 

1.02 

0.54 

0.85 

1 

3.5 

6.0 

1.77 

0.97 

0.51 

0 89 

1 

3.5 

6.5 

1.92 

0.93 

0.49 

0 92 

1 

3.5 

7.0 

2.06 

0 89 

0 47 

0.95 

1 

3.5 

7.5 

2.21 

0.86 

0.45 

0.98 








1 

4.0 

6.0 

1.57 

0.92 

0.56 

0 84 

1 

4.0 

6.5 

1.7 

0 

0.88 

0.53 

0.87 

1 

4.0 

7.0 

1.83 

0.84 

0.51 

0 90 

1 

4.0 

7.5 

1.96 

0.81 

0.50 

0.93 

1 

4.0 

8.0 

2.10 

0.78 

0.48 

0.95 

1 

4.0 

8.5 

2.2 

3 

0.76 

0.46 

0.98 








1 

5.0 

9.0 

1.94 

0.67 

0.52 

0.93 

1 

5.0 

10.0 

2.15 

0.63 

0.48 

0.96 

1 

6.0 

11.0 

2.04 

0.56 

0.52 

0.94 

1 

6.0 

12.0 

2.22 

0.54 

0.49 

0.98 

1 

7.0 

13.0 

2.07 

0.48 

0.51 

0. 95 

1 

7.0 

14.0 

2.23 

0.46 

0.49 

0. 98 













































































































































































6106 


THE MATERIALS OF CONSTRUCTION. 


PROPORTIONS OF MATERIALS IN CEMENT CONCRETE, MODERATELY 

rammed . (Continu ed.) 



Concrete with 2^-incli Stone, 

Screened. 

Concrete with Gravel £ Inch and Under. 

Proportions of Mixture. 

Required for 1 Cubic 
Yard. 

Proportions of Mixture. 

Required for 1 Cubic 
Yard. 

Cement. 

Sand. 

Stone. 

Ratio: 

Store 

Mortar' 

Cement. 

Barrels. 

Sand. 

Cubic 

Yards. 

Stone. 

Cubic 

Yards. 

Cement. 

Sand. 

> 

c3 

3 

Ratio: 

Gravel 

Mortar' 

Cement. 

Barrels. 

Sand. 

Cubic 

Yards. 

Gravel. 

Cubic 

Yards. 

1 

1 

2.0 

1.42 

2.72 

0.41 

0.83 

1 

. 

2.5 

1.79 

2.10 

0.32 

0.80 

1 

1 

2.5 

1.79 

2.41 

0.37 

0.92 

1 

1 

3.0 

2.14 

1.89 

0.29 

0.86 

1 

1 

3.0 

2.14 

2.16 

0.33 

0.98 

1 

1 

3.5 

2.50 

1.71 

0.26 

0.91 








1 

1 

4.0 

2.86 

1.55 

0.24 

0.94 

1 

1.5 

2.5 

1.40 

2.16 

0.49 

0.82 

1 

1.5 

3.0 

1.68 

1.71 

0.39 

0.78 

1 

1.5 

3.0 

1.68 

1.96 

0.45 

0.89 

1 

1.5 

3.5 

1.97 

1.57 

0.36 

0.83 

1 

1.5 

3.5 

1.97 

1.79 

0.41 

0.96 

1 

1.5 

4.0 

2.25 

1.46 

0.33 

0.88 

1 

1.5 

4.0 

2.25 

1.64 

0.38 

1.00 

1 

1.5 

4.5 

2.53 

1.34 

0.31 

0.91 








1 

1.5 

5.0 

2.81 

1.24 

0.28 

0.94 

1 

2.0 

3.0 

1.38 

1.78 

0.54 

0.81 

1 

2.0 

3.5 

1.61 

1.44 

0.44 

0.77 

1 

2.0 

3.5 

1.61 

1.66 

0.50 

0.88 

1 

2.0 

4.0 

1.84 

1.34 

0.41 

0.81 

1 

2.0 

4.0 

1.84 

1.53 

0.47 

0.93 

1 

2.0 

4.5 

2.07 

1.26 

0.38 

0.86 

1 

2.0 

4.5 

2.07 

1.43 

0.43 

0.98 

1 

2.0 

5.0 

2.31 

1.17 

0.36 

0.89 








1 

2.0 

6.0 

2.77 

1.03 

0.31 

0.94 

1 

2.5 

3.5 

1.37 

1.51 

0.5S 

0.81 

1 

2.5 

4.0 

1.57 

1.24 

0.47 

0.75 

1 

2.5 

4.0 

1.57 

1.42 

0.54 

0.87 

1 

2.5 

4.5 

1.76 

1.16 

0.44 

0.80 

1 

2.5 

4.5 

1.76 

1.33 

0.51 

0.91 

1 

2.5 

5.0 

1.96 

1.10 

0.42 

0.83 

1 

2.5 

5.0 

1.96 

1.26 

0.48 

0 96 

1 

2.5 

5.5 

2.16 

1.03 

0.39 

0.86 

1 

2.5 

5.5 

2.16 

1.18 

0.44 

0.99 

1 

2.5 

6.0 

2.36 

0.98 

0.37 

0.89 








1 

2.5 

7.0 

2.75 

0.88 

0.33 

0 93 

1 

3.0 

4.0 

1.34 

1.32 

0.60 

0 80 

1 

3.0 

5.0 

1.68 

1.03 

0.47 

0.78 

1 

3.0 

4.5 

1.51 

1.24 

0.57 

0.85 

1 

3.0 

5.5 

1.85 

0.97 

0.44 

0.81 

1 

3.0 

5.0 

1.68 

1.17 

0.54 

0.89 

1 

3.0 

6.0 

2 02 

0.92 

0.42 

0.84 

1 

3.0 

5.5 

1.85 

1.11 

0.51 

0.93 

1 

3.0 

6.5 

2.18 

0.88 

0.40 

0.87 

1 

3.0 

6.0 

2.02 

1.06 

0.48 

0.97 

1 

3.0 

7.0 

2.35 

0.84 

0.38 

0.89 








1 

3.0 

7.5 

2.52 

0 80 

0.37 

0.91 








1 

3.0 

8.0 

2.68 

0.76 

0.35 

0.93 

1 

3.5 

5.0 

1.48 

1.11 

0.59 

0.85 

1 

3.5 

6.0 

1.77 

0.88 

0.46 

0.80 

1 

3.5 

5.5 

1.63 

1.06 

0.56 

0.89 

1 

3.5 

6.5 

1.92 

0.83 

0.44 

0.82 

1 

3.5 

6.0 

1.77 

1.00 

0.53 

0.92 

1 

3.5 

7.0 

2.06 

0.80 

0.43 

0.85 

1 

3.5 

6.5 

1.92 

0.96 

0.51 

0.95 

1 

j 

3.5 

7.5 

2.21 

0 76 

0.41 

0 87 

1 

8.5 

7.0 

2.06 

0.91 

0.49 

0.98 

1 

3.5 

8.0 

2.36 

0.73 

0.39 

0.89 


' 






1 

3.5 

8.5 

2.51 

0.71 

0.38 

0.91 








1 

3.5 

9.0 

2.65 

0.68 

0.36 

0.92 

1 

4.0 

6.0 

1.57 

0.95 

0.58 

0.87 

1 

4.0 

7.0 

1.63 

0.77 

0.47 

0.81 

1 

4.0 

6.5 

1.70 

0.91 

0.55 

0.90 

1 

4.0 

7.5 

1.96 

0.73 

0.44 

0.83 

1 

4.0 

7.0 

1.83 

0.87 

0.53 

0.93 

1 

4.0 

8.0 

2.11 

0.71 

0.43 

0.86 

1 

4.0 

7.5 

1.96 

0 84 

0.51 

0.96 

1 

4.0 

8.5 

2.23 

0.68 

0.42 

0.88 

1 

4.0 

8.0 

2.11 

0.81 

0.49 

0.98 

1 

4.0 

9.0 

2.36 

0.65 

0.40 

0.89 








1 

4.0 

9.5 

2.49 

0.63 

0.38 

0.91 








1 

4.0 

10.0 

• 

2.62 

0.61 

0.37 

0.93 

1 

5.0 

8.0 

1 72 

0 74 

0.57 

0.91 

1 

5.0 

10.0 

2.15 

0.57 

0.43 

0.87 

1 

5.0 

9.0 

1.94 

0.70 

0.53 

0.96 1 

. .. 

1 

5.0 

12.0 

2.58 

0.51 

0.38 

0.92 

1 

6.0 

9.0 

1.67 

0.65 

0.59 

0.89 

1 

6.0 

12.0 

2.22 

0.48 

0.44 

0.88 

1 

6.0 

10.0 

1.85 

0.62 

0.56 

0.93 

1 

6.0 

14.0 

2.59 

0.43 

0.40 

0.92 

1 

7.0 

11.0 

1.75 

0.54 

0.58 

0.91 

1 

7.0 

14.0 

2.22 

0.42 

0.44 

0.83 

1 

7.0 

12.0 

1.91 

0.52 

0.55 

0.95 

1 

7.0 

16.0 

2.54 

0.38 

0.40 

0.92 







































































































































































































TESTS ON CEMENTS , CEMENT-MORTARS, AND CONCRETES. 611 

25 per cent stronger but 12 per cent more expensive for a given strength, 
while a mixture of 1 0. : 4 S. : 10 stone is 12 per cent weaker and about 10 
per cent more expensive for a given strength, than the mixture 1 C. : 3 S. 
: 7J stone, all by volume. 



PlG. 552.—Economy in Portland-cement-concrete Mixtures as shown by Tests of Con¬ 
crete Beams. Each result the mean of two tests on beams 10 in. square. Cement 
$3.00 per bbl.; sand $0.50 and stone $1.00 per cu. yd. (Wheeler, Rep Chf. Engrs. 
1895, p. 2926.) 

In Fig. 553 are shown the results of tests on Portland-cement concrete 
beams where the mcrtar was always the same (1 C. : 3 S.), while the stone 
ingredient varied. Results are here shown for an age of one year and also 
of 22 months. It is very noticeable that the strength at 22 months is much 
greater (about 60 per cent greater) than at 12 months. This apparently 
great increase in strength may be partly due to the shorter length of beam, 
this being but 20 inches between supports, as compared with 48 inches for 
the 12-month tests. 

Here again the maximum economy is found for the mixture 1 C. : 3 S. 
: 7£ stone, as shown by the curve marked “Ratio of cost to strength.” For 
this mixture the voids are just filled, while with a less amount of stone there 
is an excess of mortar, and with a greater proportion the voids are not filled. 































612 


THE MATERIALS OF CONSTRUCTION. 


In the case of natural-cement mortar, the cost of the cement being now $1.30 
per barrel instead of $3.00, the most economical mixture is about 1 C. : 14 
S. : 4 stone, as shown by Fig. 554. The data on these mixtures were as 
follows: 


Mixture. 

Cost per Cubic Yard in 
Dollars. 

Cross-breaking Modulus in 
Pounds per Square Inch. 

1 C. 

: f S. 

: H S. 

: 21 S. 

: 3 S. 

: 3 Stone. 

4.05 

420 

1 c. 

: 4 Stone. 

3.20 

332 

1 c. 

5.9 Stone. 

2.70 

240 

1 c. 

7.4 Stone. 

2.40 

186 




The effect of making a portion (13 per cent) of the broken stone consist 
of screenings, such as are formed when a rock-crusher is employed, is shown 
in Fig. 553. This is very marked where there is a deficiency of mortar. 



Fig. 553.—Strength of Portlaud-cement-concrete Beams. Effect of Varying Propor¬ 
tions of Stone to 1 of Cement, always using 3 Sand to 1 Cement. Each result is the 
mean of two tests on beams 10 in. square. Stone passed 1-in. screen and stopped on 
f-iuch. Cement $3.00 per bbl.; sand $0.50 and stone $1.00 per cu. yd. (Wheeler, 
Rep. Chf. Engrs. 1895, p. 2924.) 


Thus with the mixture 1C. : 3 S. : 11.4 stone the strength was increased 
about 25 per cent by making the broken stone consist of 13 per cent screen¬ 
ings. Where the mortar is sufficient to fill the voids of the stone or gravel 
the fine screenings would weaken the concrete, as they would be equivalent 
to so much additional sand. 

420. Filtration through Concrete.— In Fig. 555 are given results of fil¬ 
tration experiments on Portland-cement concrete of different mixtures. The 
most remarkable feature of this diagram consists in the evidence it offers of 

the rapid closing of the openings in the mass. At the end of 18 davs the 

«/ 











































TESTS ON CEMENTS , CEMENT MORTARS, AND CONCRETES. 613 


filtration had practically ceased in all the mixtures, although the concrete 
was three months old when the experiments began. Whether this rapid 
diminution in the rate of filtration is due to the progressive crystallization 
of the cement as a result of the flow of water through it or from some other 
cause does not appear. It is commonly accepted that the disintegration of 
Portland-cement concrete is primarily due to its permeability, and hence 
filtration tests are made to determine this property. As all of the mixtures 
shown in Fig. 555 become practically impervious to water in a few days, they 
should be considered as entirely satisfactory on this score. 



Fig. 554.—Economy in Natural-cement-concrete Mixtures as shown by Tests of Con¬ 
crete Beams. Each result is the mean of two tests on beams 10 in. square and 
nineteen months old. (Wheeler, Rep, Chf. Engrs. 1895, p. 2929.) 

421. The Effects of Freezing on Cement-mortars and Concretes.— The 

disintegration of cement-mortars and concretes by frost is due to the expan¬ 
sive force of ice. If the free water in cement-mortar freezes before it be¬ 
comes combined by crystallization in the process of hardening, evidently 
this mortar cannot set or harden until the ice melts. But when the tem¬ 
perature is low or near that of freezing the hardening action is very small, so 
that the mortar is likely to dry out before the water present is taken up by 
the hardening cement. In this case it will never harden, and this is apt to be 
the case with the outer or exposed portions of cement-masonry. Again, when 
the cement has set and partially hardened, if the freezing of the remaining 
water (or of that which the porosity of the mortar allows to enter it from 
without) produces an expansive force in excess of the cohesive strength of 
the mortar at the time, then the bond is broken by the expanding ice, and 
















614 


THE MATERIALS OF CONSTRUCTION. 


on thawing out the mortar crumbles from the disintegrating action of the 
frost, the same as a soft, porous stone or brick will do. Portland-cement 
mortar being stronger than that made with natural cement, it resists this- 
disintegrating action better, and hence the general assumption that Portland 
cement may be used in freezing weather and natural cement may not. 


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Fig. G55.—Filtration of Sea-water through 1 cu. ft. of Portland-cement Concrete, Three 
Months Old, uuder 24 ft. head. (Inst. Civ. Engrs., vol. cvn. p. 95.) 


The Universal Rule to be followed when using cement in freezing weather 
is to use the minimum amount of water in gauging the mortar, to keep it 
from freezing until it has acquired a considerable strength, and to protect it 
from the weather or from the action of alternate wettings and freezings. It 
should also be made richer in cement than that used at ordinary tempera¬ 
tures. There are various ways of preventing freezing, as, for example: 






















TESTS ON CEMENTS , CEMENT-MORTARS, AND CONCRETES. 615 

1. Warming the water or sand or stone, or all of them, as occasion seems 
to require. 

2. In very cold weather, in addition to the provisions in (1), the work 
may be covered with earth or manure, or housed and a fire maintained, etc, 

3. In place of these methods of maintaining a temperature above the 
freezing-point, the water may be dosed with salt or glycerine or alcohol, 
until it will not freeze at the temperatures anticipated. 

All of these methods are used and all are satisfactory. The cheapest and 
most common method is to make a brine of the water used in gauging the 
mortar. In. Fig. 556 the proper percentages of salt, glycerine, and alcohol 



Fig. 556.—Effect on the Freezing-point of Cement of Various Proportions of Glycerine, 

Alcohol, and Salt. (Tetmajer, vol. vii. p. 85.) 


are shown to prevent freezing at the various temperatures from 32° to 0° F. 
From this it appears that salt is the most efficient agent as well as the 
cheapest. From this diagram we have, approximately, 


No. degrees F. f reezing temp, is reduced = per cent salt used. 


Thus if it is assumed that the temperature will not fall below 22° F., then 
10 per cent (by weight) of salt should be added to the water. If a tempera¬ 
ture of 10° F. is to be provided for, use 22 per cent of salt. Doubtless a 
less proportion of salt would prove effective at these temperatures, especially 
with concrete in large masses, as the chemical reactions which accompany 
the hardening of the cement develops a considerable amount of sensible heat. 
(See Art. 312 and Figs. 333 and 333a.) 

Any cement sets very much slower at a low temperature than at a higher, 
as is shown by Fig. 557, which is complementary to Fig. 333, p. 414. Thus 
a mortar which will set completely (by the method of testing employed) 
in four hours at a temperature of 35° C. (95° F.) would require twenty 
hours at 5° C. (41° F.) and thirty-eight hours at 0° C. (32° F.). In 
estimating the time required tor setting, therefore, this tempciatuie-effect 
must be allowed for. 

In Fig. 558, upper half, is shown the effect of salt on tension briquettes 


























616 


TIIB MATERIALS OF CONSTRUCTION. 


of Portland cement which were moulded in a room where the temperature 
was 8° F. (24° F. below freezing), and where the briquettes were frozen hard 
in half an hour, and remained frozen GO days. They remained in the open 
air and hardened when they thawed out. It should be noted that the 
briquettes grew weaker between the ages of 64 and months. 

In the lower half of this figure are given the results of tests of the same 
cement-mortar moulded in air at a temperature of 21° F., and left frozen 
for three days and then placed under water for the remaining period. 



In the former series (hardened in air) we might conclude that more than 
5 or 10 per cent of salt weakened the mortar somewhat, while in the latter 
(hardened in water) the briquettes increased in strength up to 20 per cent 
salt. This is, furthermore, a more typical case. Cement-masonry is not 






































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 617 

likely to be laid in extremely cold weather or when such weather is likely 
to occur before the cement has set. 

The worst set of conditions for cement-mortar to withstand is that of a 
succession of temperatures below and abov r e the freezing-point. If the 
mortar freezes as soon as laid, there is no bond to be broken, and no injury 
can result provided that when it thaws out it remains unfrozen long enough 
to harden. But if it begins to set and then freezes again before the cohesive 
strength can resist the expansive force of the frost, then it is cracked and 
these severed surfaces will never again unite. Water then enters such 
cracks and further disintegration follows. 



Fig. 558.—Effect of Salt on Portland-cement Mortar, 1C.: 2 8., made in Freezing 
Weather. (Wheeler, Rep. Chf. Engrs. 1895, p. 2968.) 


A careful distinction must be drawn between contraction cracks, which 
may always be found in long masonry walls in cold weather, and disentegra- 
tion cracks from the expansive force of water freezing on the interior. 

In Fig. 559 the effect of salt on the strength of both natural- and Port- 
land-cement mortar is shown. These briquettes were not subjected to freez¬ 
ing temperatures, and hence the results are not very significant. These and 
similar tests simply determine whether or not the salt weakens the mortar if 
used at temperatures above freezing. But as it is never used in this way the 
results are scarcely to the point. 

Similar to these are the results shown in Fig. 560, except that all these 
were made with a saturated solution of salt (about 30 per cent), and with 
different proportions of sand, up to 2 S. : 1 C., which is as much sand as 
should be used in freezing weather. 


























618 


THE MATERIALS OF CONSTRUCTION. 



Fig. 559.—Effect of Salt on Strength of Cement-mortar Six Months Old. (Jour. Assoc r 

Eng. Socs., vol. ix.) 




Fig. 560.—Tensile Strength of Quartz Fig. 561 —Effect of Salt on Portland-cement 
and Sand Mortars with a Saturated Mortar, 1C.: 2 S., made in Freezing Weather. 

Solution of Salt. (R. R. Gazette, (Wheeler, Rep. Chf. Engrs. 1895, p. 2971.) 

1892.) 
























































TESTS ON CEMENTS CEMENT-MORTARS, AND CONCRETES. 619 

In Fig. 561 we have the extreme conditions of fresh water and a brine 
containing 20 per cent salt, used in making up Portland-cement-mortar 
briquettes in a room temperature of 13° to 16° F. (at which the 20-per-cent 
salt-mixtures would not freeze), and left at this temperature for three days. 
Then 40 of these briquettes were placed in water and the remaining 40 were 
stoied in the open air. Phis being early in January at Lake Superior, it is 
likely the “ air ” briquettes remained frozen for some months. When they 
did thaw out, the temperature conditions seem to have been favorable to their 
hardening. Probably they had so dried out while frozen that there was 



Fig. 562.—Use of Salt iu Portland-cement Mortar, 1 C. : 1 S. and 1 C. : 4 S. Those 
left in air remained frozen about sixty days. Those put iu water were first frozen 
in air three days. (Wheeler, Rep. Chf. Engrs. 1895, p. 2970.) 

not sensible moisture enough to produce expansion by successive freezing 
and thawing. It is to be presumed they were not exposed to the weather, 
but were at least under shelter. It is a common maxim with civil engineers 

o 

of large experience in such matters that if cement-masonry, laid in freezing 
weather, remains frozen till dry, or if it “ freezes dry,” it will harden with¬ 
out injury, but if it freezes and thaws sucessively while yet “green” it will 
be injured, if not ruined. 

In Fig. 562 are shown results on two mixtures, 1 C.: 1 S., and 1 C.: 4 S. 






















620 


THE MATERIALS OF CONSTRUCTION. 


These briquettes were made up at 18° F. (at which temperature the 
15-per-cent salt-mixtures would scarcely freeze), and the “ air ” briquettes 
put in the “ open air ” after three days, this being early in January, 1894, 
at Lake Superior. Even the 15-per-cent-salt briquettes doubtless were 



frozen on being put out in the open air. The results are not such as to lead 
to any positive conclusion. 

Prof, von Tetmajer has experimented largely with anti-freezing solutions 































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 621 

ior mixing cement-mortars, those of salt on Portland-cement mortars being 
shown in big. 503, and on natural-cement mortars in Fig. 5G4.' All these 
tests were made at the standard temperature of G5° F., so that they show 
simply the effect of the salt on the tensile and the compressive strength, 
when hardened in air and under w T ater. In every case any addition of salt 
weakened the mortar, an addition of 6 per cent of salt reducing the strength 




Fig. 564.—Effect of Salt on the Hardening of Natural-cement Mortar 1 C / 3 S. 

(Tetmajer, vol. vii. p. 34.) 

about 25 per cent. The reduction was more marked with the natural- than 
with the Portland-cement mortars. 

In Figs. 565 and 565a Tetmajer gives us similar results on Portland- 
cement mortars of anti-freezing mixtures of solutions of glycerine and of 
alcohol. In every instance these ingredients also weakened the mortar. 





































































622 


THE MATERIALS OF CONSTRUCTION. 



I OOF 





















































































































TESTS ON CEMENTS, CEMENT-MORTARS, AND CONCRETES. 623 


422. Concrete Mixtures should be so proportioned as to produce as 
nearly as possible a solid mass with the least proportion of cement. Broken 
stone is not at all essential to a first-class concrete, a clean gravel serving 
quite as well. Thus Col. G. Ii. Mendell gives the following formula with 


the resulting volumes at each stage *: 

Cubic Feet. 

One barrel of Portland cement, measured loose. 4.50 

Water added. 188 

Volume of paste. 3,90 

Sand equal to three times the volume of paste. 11.70 

Water added. 2.25 

Volume of mortar. 11.21 

Gravel, 3/4 in. and less. 36.70 

Volume of loose concrete.44.24 

Final volume tamped in place... .. 36.20 


Here we have 51.9 cubic feet of loose solids finally compacted to a volume 
of 36.2 cubic feet, or to 69 per cent of the loose volumes when measured 
separately. 

423. Concrete Structures in Sea-water. —On the subject of the perma¬ 
nency of cement-concrete when exposed to the action of sea-water Dr. 
Michaelis, the highest possible authority, says f : 

“ The main points to be considered in erecting permanent structures in 
sea-water with the aid of hydraulic cements—in other words, concrete—are: 

“ (1) From the physical point of view, completely impermeable mixtures 
should be made, composed of one part of cement with two or at the most 
two and a half parts of sand, of mixed grain, of which at least one third 
must be very fine sand. To this the requisite quantity of gravel and ballast 
should be added. This impermeable layer should surround the porous 
kernel on all sides in sufficient thickness, even underneath. It would, per¬ 
haps, be unnecessary waste of material, in the case of thick walls, to use 
the impermeable mixture throughout; but, so far as possible, the compact 
shell and the poorer kernel should be made in one operation. Where this 
is not possible, and the shell is added subsequently, numerous iron ties 
should be used. 

“ (2) From the chemical point of view, cements or hydraulic limes rich 
in silica, and as poor as possible in alumina and ferric oxide, should be used, 
for aluminate and ferrate of lime are not only decomposed and softened 
rapidly by sea-water, but they also give rise to the formation of double com¬ 
pounds which in their turn destroy the cohesion of the mass by producing 
cracks, fissures, and bulges. The salts contained in sea-water, especially the 
sulphates, are the most dangerous enemies of hydraulic cements. The lime 


* In Jour. Assc. Eng. Socs., vol. xiv. p. 243. 
f In Trans. Inst. Civ. Engrs., vol. evil. p. 375. 














624 


THE MATERIALS OF CONSTRUCTION. 


is either dissolved and carried off by the salts, and the mortar thus loosened, 
or the sulphuric acid forms with it crystalline compounds as basic sulphate 
of lime, alumino-sulphate and ferro-sulphate of lime, which are segregated 
forcibly in the mortar, together with a large quantity of water of crystalliza¬ 
tion, and a consequent increase in volume results. The separation of hy¬ 
drate of magnesia is only the visible but completely innocuous sign of these 
processes. The magnesia does not in any way enter into an injurious reac¬ 
tion with silica, alumina, or ferric oxide; it is only displaced by the lime 
from its solution in the shape of a flocculent, slimy hydrate which may be 
rather useful in stopping the pores, but can never cause any strain or ex¬ 
pansion, even if it subsequently absorbed carbonic acid. 

“ The carbonic acid, whether derived from air or water, assists the hy¬ 
draulic cement as a preservative wherever it comes into contact with the 
solid mortar. It could only loosen the latter if present in such an excess 
that bicarbonate of lime might be formed. 

“ (3) The use of substances which render the mortar, at any rate in its 
external layers, denser and more capable of resistance. Such substances are: 

“ (rt) Sesquicarbonate of ammonia (from gas-liquor) in all cases where 
long exposure to the air is impossible. Such a solution, applied with a 
brush or as a spray and then allowed to dry, converts the hydrate of lime 
into carbonate of lime. The latter is not acted upon by the neutral sul¬ 
phates present in sea-water. It must be repeated that it is a decidedly errone¬ 
ous opinion that the texture of otherwise sound cements is injured by the 
action of carbonic acid; on the contrary, it renders them more capable of 
resistance, except in the above-mentioned case, which is extremely rare 
when bicarbonate of lime is formed and goes into solution. 

“ (b) Fluosilicates, among which magnesium fluosilicate is most to be 
recommended. The free lime is converted into calcium fluoride and silicate 
of lime, and, in conjunction with the liberated hydrate of magnesia, these 
new products close the pores of the mortar. Both salts are sufficiently 
cheap to be used on a large scale. 

“ ( c ) Last, not least, barium chloride. Two or three per cent of the weight 
of the cement is dissolved in the water with which the concrete is mixed. 
This forms perfectly insoluble barium sulphate with the sulphates of the 
sea-water, while the magnesia remains in solution as magnesium chloride. 
Although in this case there can be no further closing of the pores, yet the 
insoluble barium sulphate which is formed affords some protection and does 
not give rise to any increase of volume (swelling). From two to three per cent 
of barium chloride does not in any way diminish the strength, as has been 
proved by means of comparative tests of English and German cements. 
Frequently the strength of the mortar is increased by this addition. This 
substance is only to be used in the external, perfectly water-tight skin of the 
concrete; in other words, in the 4- to 8-inch coating, composed of 1 cement, 

1 to 2 sand, and 3 to 4 coarse gravel, flint, broken stone, etc.” 


TESTS ON CEMENTS, 


CEMENT-MORTARS, AND CONCRETES. 


625 


TABLE 


XXXVIII.—TESTS OF THE FIRE-RESISTING 

KINDS OF CONCRETE. 


QUALITIES OF DIFFERENT 


(Hamburg Commission Report, 1895.) 


Num¬ 
ber of 
Test. 

I. 

Composition of 
Concrete. 

Time of 
Heat- 
ing. 

Manner of 
Cooling. 

Result of Heating. 

Result of 
Wetting after 
Heating. 

Temperature 
measured by 
Pyrometer. 

Highest tempera¬ 
ture 1000° c. 

1 part cement. 
7 parts river- 
gravel. 

3 H 

Suddenly. 

Broken. 

Crumbled en¬ 
tirely. 

Slowly. 

“ 

i 4 

44 

II. 

1 part cement, 
8 parts river- 
gravel. 

m 

Suddenly. 

44 

" 

44 

Slowly. 

44 

* 4 

44 

III. 

1 part cement, 
3 parts sand, 

5 parts broken 
stone. 

m 

Suddenl}’. 

Not broken.but mortar 
very tender. 

Lost coherence 

44 

Slowly. 

it 

4 • 

44 

IV. 

1 part cement, 

7 parts washed 
bank-gravel. 

m 

Suddenly. 

Showed very little co¬ 
herence. 


44 

Slowly. 

it 


ik 

V 

1 part cement, 

8 parts washed 
bank-gravel. 

i 

Suddenly. 

11 

Crumbled. 

After 1 hour 780° C. 

Slowly. 

it 

44 

44 

VI. 

1 part cement, 

7 parts fine cin¬ 
der. 

m 

Suddenly. 

Not broken, but broke 
upon striking. 

Showed good 
coherence; 
did not suffer. 

After 1J4 hours 
780° C. 

Slowly. 

41 

44 

Highest tempera¬ 
ture 1080° C. 

VII. 

1 part cement, 

8 parts fine cin" 
der. 

m 

Suddenly. 

44 

*4 

After hours 

780° C. 

Slowly. 

4 4 

44 

Highest tempera¬ 
ture 1080° C. 

VIII. 

1 part cement, 

7 parts coarse 
cinder. 

m 

Suddenly. 

Not broken; showed 
relatively rhe highest 
degree of coherence, 
particularly in the 
centre. 

Did not suffer. 

44 

Slowly. 

44 

44 

44 

IX. 

1 part cement, 

3 parts coarse 
cinder. 


Suddenly. 

4 4 

4 4 

Highest tempera¬ 
ture 940° C 

Slowly. 

44 

Did not suffer; 
friable edges. 

44 

X. 

1 part cement, 

3 parts sand, 

5 parts broken 
basalt. 

3J4 

Suddenly. 

Not broken, but broke 
upon striking. 

Crumbled. 

4 

Slowly. 

Broken. 

Coherence very 
slight. 

44 

XI. 

1 part cement, 

7 parts sand. 

3J4 

Suddenly. 

Broken in 3 pieces. 

Low degree of 
coherence. 

44 

Slowly. 

Broken; very tender. 


44 

XII. 

3 parts Trass- 
mortar,* 

5 parts cinder. 

3 

Suddenly. 

Broke in taking out. 

Crumbled com¬ 
pletely. 

44 

Slowly. 

Broken; very tender. 


44 

XIII. 

part Trass, 

2 parts slacked 
lime, 

20 parts river- 
gravel. 

3^ 

Suddenly. 

Completely broken. 


44 

Slowly. 

Crumbled to powder. 


44 


* Trass-mortar = 1 part Trass, 2 parts slacked lime, 3 parts sand. 





































































































































































































626 


THE MATERIALS OF CONSTRUCTION. 


TESTS OF THE FIRE-RESISTING QUALITIES OF CONCRETE— Continued. 


Num¬ 
ber of 
Test. 

Composition 
of Concrete. 

Time of 
Heat¬ 
ing. 

Manner of 
Cooling. 

Result of Heating. 

Result of 
Wetting after 
Heating. 

Temperature 
measured by 
Pyrometer. 

XIV. 

1 part cement, 

7 parts pumice- 
sand. 

3^ 

Suddenly. 

Not broken; showed 
some coherence, par¬ 
ticularly in centre. 

Outer part ten¬ 
der, and pieces 
fell off. 

Highest tempera¬ 
ture 940° C. 

Slowly. 

Not broken.' 

Friable on 
edges. 

4 4 

XV. 

1 part cement, 

3 parts sand, 

5 parts grit¬ 
stone. 

3y a 

Suddenly. 

Fell to pieces upon 
touching. 

Crumbled en¬ 
tirely. 

44 

Slowly. 

Broken. Coherence al¬ 
most completely lost. 


44 

XVI. 

7 courses of 
brick (one 

brick deep) 
in cement- 
m^rtar * 

314 

Suddenly. 

Mortar very tender 
and lost its binding 
power; some bricks 
cracked. 


44 

Slowly. 



44 


* Cement-mortar 1 to 3. 


424. The Fire-resisting Qualities of Concretes. —Since concrete con¬ 
struction is now used very largely in large buildings, its fire-resisting 
qualities become of supreme importance in such works. The most 
elaborate investigations ever made into these qualities of various concrete 
mixtures was carried out by a commission especially appointed by the city 
of Hamburg, Germany, for this purpose some years ago, and who issued an 
elaborate report in 1895.* Table XXXVIII embodies their results on fire- 
tests of sixteen different concrete mixtures. 

It will be observed that all the sand, gravel, stone, and fine-cinder con¬ 
cretes failed to stand the test. Only the coarse-cinder concrete (1 C. to 7 
or 8 cinder) gave good results. Even the wetting while hot did not affect 
it. It would seem, therefore, that a screened-cinder concrete would give 
excellent results. 

Hydraulic cements, both natural and Portland, harden partially by 
crystallization, requiring the combination with an amount of water equal to 
some 15 per cent of the weight of the pure cement. When this partially 
crystallized mass is highly heated the water of crystallization is driven off 
and a portion of the cement is reduced to an inert mass or powder. A high 
heat long continued, therefore, weakens the strength of all cement mortars 
and concretes. 

Mr. J. S. Dobie has found f that neat Portland-cement briquettes two 
months old, gradually heated to 1000° F. and then removed from the fur¬ 
nace and allowed to cool in the air, lose about 10 per cent of their weight 

* Results of tests upon various kinds of patented heat insulating systems of protect¬ 
ing the iron framework of a building are also given in this report. 

f In the Digest of Physical Tests, vol. i. p. 212 (1896). 

















































TESTS ON CEMENTS, CEMEMT-MORTARS, AND CONCRETES. 627 


and 50 per cent of their tensile strength. If heated suddenly to 1775° F. 
and cooled in the air, they lost 10 per cent of their weight and 80 per cent 
of their strength, the results in both cases, however, being far from uni¬ 
form. When plunged in water on removing them from the furnace, they 
fell to pieces in both instances. 

Mr. T. T. Johnston has shown* that for natural- and Portland-cement 
briquettes, both neat and 1 C. : 1 S., heated to a dull red after thorough 
drying, gave losses of strength as follows: 

LOSS OF STRENGTH OF CEMENT-MORTAR FROM HEATING. 


Kind of Cement. 

Neat. 

Mortar. 

T^atural cement...... 

89 per cent 

58 “ “ 

(1 c. 
(1 0 . 

: 1 S.) 61 per cent 
: 3 S.) 70 “ “ 

Portlaud cement. 



It is evident, therefore, that fire-proof construction should not rely on 
a sand or stone cement-concrete for tensile strength. If it be used only in 
■compression, a metal base resisting the tensile deformations, then it may be 
able to carry its load during the fire, but it would probably require recon¬ 
struction afterwards, especially if water reached the cement portions while 
they were highly heated. 

425. Portland-cement Cinder-concretes. —The strength, weight, cost, 
and economy of a Portland-cement cinder-concrete construction in St. Louis 
in 1896, taking actual prices for large buildings and adding 5.5 cts. per cubic 
foot for laying, are shown graphically in Fig. 566. The test mixtures were 
made without special care, and had therefore much less strength than the 
same ingredients would have in practice if mechanically mixed.f The mix¬ 
tures are arranged in the diagrams in the order of their economic values, 

. . strength mi 

that is, in the order of their rank m the quality, —• L lie specimens 

were all 6 in. square and 12 in. high, and were crushed in the direction of 
the longest dimension. They were all 30 days old when tested. The 
cinders were the ordinary furnace product of St. Louis, obtained by burn¬ 
ing the Illinois bituminous coal under boilers. It is mostly a fine ash with 
considerable unburned coal in its composition. 

It will be observed that the mixture 1 cement : 1 sand : 3 cinder is at once 

both the most economical, ( stieT1 g^ _ max . \ and also the strongest for its 


* Engineering Record, vol. xxxv. p. 54. 

f The specimens were prepared under the direction of Mr. A. L. Johnson, Assoc. M. 
Am. Soc. C. E , and were tested by the author. 















628 


THE MATERIALS OF UOJVXTKUUT1UJY. 


weight, ('— 1 en ^ -~ = max3 It would seem, therefore, that where quantity 
\ weight / 

is proportioned to obtain a given strength, this w r ould be the mixture to em¬ 
ploy if cinder-concrete were to be used. 



COMPOSITION OF CONCRETE MIXTURES. 

Fig. 566.—Portland-cement Cinder-concrete. Strength, Weight, Cost, and Economy 

of, for St. Louis, 1896. Tests made by the Author. 


















































TESTS ON CEMENTS, CEMENT-MORTARS , AND CONCRETES. 629 


TABLE XXXIX.—CROSS-BENDING STRENGTH OF PORTLAND-CEMENT CINDER- 
CONCRETE MIXTURES WITH AND WITHOUT EXPANDED METAL BASE. 

Slabs 36 in. long, 12 in. wide, and 4 in. thick tested as beams on supports 32 in. apart. 

(Author’s Records.) 


Mixture. 

With or 
Without Ex¬ 
panded 
Metal Base. 

Modulus of 
Elasticity, 
Pounds per 
Square Inch. 

Modulus of 
Rupture, 

. 3 wl 

f ~ 2 6/i 2 ’ 

Pounds per 
Square Inch 

Modulus of 
Strength at 
the Apparent 
Elastic Limit, 
Pounds per 
Square Inch. 

Total Deflec¬ 
tion under 
Maximum 
Load, 
in Inches. 

1 

cement 

5 

cinder . . 


With 

970,000 

150 

150 

0.008 

1 

< < 

5 

< < 



Without 

320.000 

550 

300 

.450 

1 

4 4 

6 

4 4 



Without 

490,000 

150 

150 

.015 

1 

4 c 

6 

( 4 



With 

930,000 

450 

200 

.100 

1 

cement 

1 

sand 

: 1 cinder 

Without 

690,000 

170 

150 

.015 

1 

4 < 

1 

4 6 

: 1 

< < 

With 

1,930,000 

465 

200 

.130 

1 

4 < 

2 

4 4 

: 5 

44 

Without 

430,000 

100 

100 

.002 

1 

a 

2 

i i 

: 5 

4 4 

With 

800,000 

575 

300 

.169 

1 

< c 

3 

i i 

: 5 

4 4 

Without 

490,000 

88 

75 

.013 

1 

i < 

3 

i i 

: 5 

i 4 

With 

510,000 

370 

200 

.142 

1 

i ( 

1 

a 

: 6 

4 4 

Without 

260,000 

100 

75 

.020 

1 

64 

1 

< 4 

: 6 

( < 

With 

540,000 

445 

150 

.158 
























CHAPTER XXXI. 


RESULTS OF TESTS ON STONE AND BRICK. 

STONE.* 

426. The Structural or Building Stones consist principally of 

The Granites (including the Gneisses), 

The Limestones (including the Marbles), and 

The Sandstones (including Breccias and Conglomerates). 

The granites are unstratified, eruptive rocks, and are composed of quartz 
(pure silica, Si0 2 ) having a hardness of 7;f of feldspar (silica, alumina, 
together with potash, soda, or lime) with a hardness of 6; hornblende, hard¬ 
ness 5 to 6; and small scales of mica with a hardness of 3 (see Fig. 567). 

The limestones are stratified rocks composed of sedimentary or chemical 
deposits, of which the carbonate of lime forms the principal ingredient. 
When wholly crystalline and suitable for ornamental purposes it is called 
marble (Fig. 571). When it is composed largely of a double carbonate of 
lime and magnesia it is properly called dolomite. Some of the marbles also 
have this composition. When the stone is composed very largely of small 
shell fragments it is called oolitic limestone, Fig. 569 (from its resemblance 
to the roe of a fish). Onyx is a kind of crystalline limestone which has been 
formed wholly by chemical deposition, while stalactite and stalagmite forma¬ 
tions are also limestones; but they should never be confounded with onyx, 
however much they may resemble it when polished. 

* The material in this chapter on Stone has been partly drawn from Merrill’s Stones 
for Building and Decoration (Wiley, New York). 

f The following scale of hardness is commonly used for minerals: 

1. Easily scratched with the thumb-nail, as talc. 

2. Can be scratched by the thumb-nail, as gypsum. 

3. Not readily scratched by the thumb-nail, but readily cut with a knife, as calcite 
(calcspar, or calcium carbonate). 

4. Can be cut with a knife less easily than calcite, as fluorite (fluor-spar). 

5. Can be cut with a knife with difliculty, as apatite. 

6. Can be cut with a knife only on thin edges, as feldspar. 

7. Cannot be cut with a knife and scratches glass, as quartz. 


630 





RESULTS OF TESTS ON STONE AND BRICK. 


631 



Fig. 567.—Biotite Granite, of Hallo- 
well, Me. 


Fig. 568.—Diabase from Weehavvken, 
N. J. 



Fig. 569.—Oolitic Limestone, Southern 
Indiana and Northern Kentucky. 


Fig. 570.—Reddish Potsdam Sandstone 
New York 



Fig. 571.—Crystallized Limestone 
or Marble from Vermont. 


Fig. 572.—Brown Triassic Sandstone 
from Portland, Conn. 


Microscopic Views of Building-stones. Magnified 20 Diameters. (From Merrill’s 

Stones for Building and Decoration, 1891.) 












632 


THE MATERIALS OF CONSTRUCTION. 


Sandstones are fragmental rocks composed mostly of grains of silica, 
(quartz) which have been cemented together by a deposition of silica, 
carbonate of lime, iron oxide, or clayey matter. If the cementing material 
be silica, as in Fig. 570, the rock, while extremely durable, is very hard 
and difficult to work. Iron oxide in the cementing material gives to the 
stone a reddish or brownish color, as shown in Fig. 572; here is also car¬ 
bonate of lime and clayey matter, while the sand-grains are composed of 
both quartz and feldspar, this latter being indicated in the figure by the 
grains marked by parallel bands. This more porous and absorbent matrix 
is conducive to disintegration by water and frost, although such a stone is. 
readily worked and has been very largely used in -America. The most 
durable sand-stones (having the silica matrix) are so hard to work that 
other kinds of durable rock are generally preferred. When the sand-grains 
are so lightly attached that they will readily crumble they may be used as. 
grindstones, as the sandstone of northern Ohio near Cleveland. 

427. The Weathering of Building-stones. —This term includes the resist¬ 
ance of stones, when exposed to the weather, to all the disintegrating actions 
of heat and cold, water, frost, and chemical action, which combine in this 
climate to effect the rapid decomposition and destruction of most of the 
rocks, and of many of those which have been selected for building purposes. 
A stone building or monument should remain in good preservation for hun¬ 
dreds of years, but more commonly they begin to scale and crumble before 
they are twenty-five years old. The life of a rock may be many thousands 
of years in Egypt, or Italy, or Greece, when it would not last as many scores 
of years in the United States. U 

The chief disintegrating agent with the relatively impervious rocks is 
probably the variation of temperature, thus breaking the bond by continual 
expansions and contractions, while with the more porous and absorbent it is 
probably the freezing of the absorbed water. However, these two causes 
usually combine in this climate. 

By far the best, and perhaps the only infallible, test of the weathering 
qualities of any given rock is the examination of a ledge of it which has been 
long exposed, or of an old building, slab, or monument of the stone from the 
same quarry and ledge. Sedimentary rocks, such as the limestones, may 
differ radically in consecutive ledges, so that here the particular course, or 
ledge, must be identified. As this test cannot be applied to a new quarry 
without an exposed face,* and because this is by far the most important, 
quality of any building-stone, attempts have long been made to formulate 
artificial tests of this quality, but without any very marked success. A 
single illustration of actual weathering for many years is worth more than 


* North of the Ohio and Missouri rivers, where the face of the country has been 
scoured by glacial action these rock-exposures are common. Where the glacial erosion 
did not occur no sound rock-exposures should be expected. In the glaciated region 
the scratches and grooves of the glaciers are still plainly visible in many places. 







RESULTS OF TESTS ON STONE AND BHTCK. 


633 


.0500 


0400 


.0300 


.0000 


. 0/00 


0 


1 

So 










\i 


a> 

a 

o 

co 

'O 

a 

& 

CO 

X5 

03 

CO 

O 

G. 

s 

o 

03 

03 

o 


03 


CO 


c n 



all the artificial tests which can be applied. 
Nevertheless, when these cannot be had, some¬ 
thing may be done in the way of determining 
relative resistance to frost, as described 
below. 

428. Freezing Tests.— Specimens of the 
stone may be saturated with water and 
frozen and thawed say twenty-five times, 
after which the loss in dry weight and the 
loss in crushing strength may be determined. 
This is the method pursued by Prof. Bau- 
schinger. The loss in weight by this 
method is so insignificant (see Fig. 573) as 
to furnish a very small base from which to 
estimate the relative weathering qualities of 
the stone. At best it is but a comparative 
test, the results of tests on various kinds of 
stone being compared with each other. The 
test for strength after freezing is also quite 
as unsatisfactory, since here comparison 
must be made between different specimens 
of the same stone, and a safe conclusion 
would have to rest upon average results 
of a large number of tests, and the results 
would still be only relative. 


03 

a 


CO 

03 


03 X 


CO 


KS 

co 




03 


ci 

bb 


03 

CO 

m 

03 


03 

3 

c3 


o 

'o 

03 

.2 

i§ 

00 

5 

03 

CO 

Sm 

ei 

O 

O 


_03 

,a 


•— 

if) 


03 

.a 

ci 

if) 

I 

03 

CO 

oi 

O 

O 


2 

o 


03 


co 


03 

• rH 

a 

cS 

3) 

03 


03 


if) 


co 

to 

. f—I 

03 

a 

b£> 

03 


03 

• 

a 

c3 

if) 

a 


03 

a 

03 

bb 

03 


bD -2 


03 




si 

bb bb 


03 


03 


03 


03 


03 


Fig. 573.— 


Comparative Tests of Building-stones by Freezings and by the Sulphate-of- 
soda Test. (Ivans. Am. Soc. C. E., vol. xxxm. p. 242.) 























































I 


634 THE MATERIALS OF CONSTRUCTION. 

429. The Sulphate-of-soda Test (Brard’s process*) consists in immersing 
the sj^ecimens for a short time in a boiling solution of the sulphate of soda, 
in the form of a decahydrate, commonly known as Glauber's salt (lSa 2 S0 4 , 
10Il 2 O), and then suspending them in the air for a day in order that the 
absorbed salt may crystallize. This process is repeated daily for a week or 
more, and then the dried salt is dissolved out by soaking in water, frequently 
renewed, for a week or more. 

In making this test it is important to have a solution of the decahydrate 
which is saturated while cold or at a temperature below 80° F. The percent¬ 
age required to make a saturated solution increases from 22 per cent at 
32° F. to 120 per cent at 90° F. At about 100° F. the salt melts in its 
own combined water, and changes to the anhydrous form (Xa 2 S0 4 ), and at 
higher temperatures the anhydrous salt dissolves in water in diminishing 
proportions, reaching 12G per cent at 212° F.f. In cooling and drying, the 
decahydrate is again formed, and this crystallizes as the solution dries down 
below the saturation-point. 

As the disintegrating action of this test is manifested wholly on the sur¬ 
face, so far as the loss of weight is concerned (the specimens being washed 
after each drying), it is important that the specimens tested should have 
the same superficial area per unit of weight. This means that if the speci¬ 
mens are of the same shape they must also be of the same size. A better 
method of representing the results would be to give the loss of weight per 
square inch of surface, rather than the percentage of loss in weight as is 
commonly given. Thus in the results plotted in Fig. 573 the specimens 
weighed from 23 to 94 grams, with no information given as to their shape 
or dimensions, while the results are taken out as j:>ercentages of loss in 
weight. Evidently the smaller specimens were at a great relative dis¬ 
advantage, as their sujoerficial areas would be much greater per unit of 
weight. 

If the granites and the decomposed sandstones be omitted from the list 
of stones given in Fig. 573, the average loss of weight on the remainder by 
the sulphate-of-soda test is about six times that by the freezing test.}; 

The specimens should either be heated before immersion in the boiling 
liquid, or they should be immersed before the liquid has come to the boiling 
temperature. The time of immersion need not be over 30 minutes, after 
which the specimens should be freely suspended in the open air for 24 hours. 
They are then sprayed from a wash-bottle and again immersed and boiled, 
this process being repeated for any desired number of times, generally from 
7 to 10. The specimens should be small, about one-incli cubes being a suit- 


* An. de Chem. et de Phys., vol. xxxvm. p. 160, 1828, afterwards modified by 
d’Hericart and de Tlmry. See Trans. Am. Soc. C. E., vol. xxxm. p. 246. 
f See Fig. 21, p. 133, of Newth’s Inorganic Chemistry. 

\ This agrees with comparative results obtained by Mr. E. Gerber, Trans. Am. Soc. 
C E, vol. xxxm. p. 253. 



RESULTS OF TESTS ON STONE AND BRICK. 


635 


able size, as the weighings have to be done with great care on delicate 
balances to secure reliable results. * 

J he specimens must be carefully dried, for 24 hours, at a temperature 
above boiling, before the first weighing and after the long soaking in fresh 
water subsequent to the tests. Any neglect of this precaution may entirely 
vitiate the results because of the relatively large amount of water absorbed 
by the stone. 

AV liile this test may do injustice to some stones (possibly because of some 
chemical action upon them) which may resist weather exposure better than 
might be determined from these results, yet it seems to be the best artificial 
means of indicating a tendency to disintegrate on exposure which has yet 
been found. But, as compared to examples of actual exposure for long 
periods of time, it should be regarded as of no weight whatever. 

430. Chemical Tests of stone are of little value in themselves, but taken 
in connecion with tests of strength, absorption, frost, and especially in con¬ 
nection with microscopical examinations, they may be of considerable value. 
In fact, as a general rule no chemical test need be made unless it is required 
to explain the microscopic structure, already examined as described in the 
following article. 

431. The Microscopic Test consists in the preparation of very thin slices 
or sections of the stone and examining these under a microscope. A thin 
chip of the stone is first ground with emery to a plane on one side and 
polished. This side is then glued to a piece of glass with Canada balsam, 
and the other side ground and polished in a similar manner. The section is 
made so thin that it is quite translucent and sufficiently transparent to read 
a printed text through it. It is then mounted regularly upon a microscope- 
slide, and covered in the usual manner. 

The examination under the microscope (magnifying about 25 diameters) 
consists in— 

1. The observation of the structural arrangement. 

2. The identification of its constitutent parts (by an experienced lithol¬ 
ogist). 

3. A study of the character of the cementing bond. 

Thus, Fig. 567 * reveals a granite of very complex structure, wholly crys¬ 
talline (though the crystals are greatly distorted), composed of quartz, several 
kinds of feldspar, and two kinds of mica. There may also be identified a 
crystallized phosphate of lime (apatite), in small needles, grains of iron ore, 
and occasionally small garnets. 

Fig. 568 shows a wholly crystalline rock, with the crystals more perfect 
and much more firmly interlocked than those in Fig. 567. There are no 
openings found, and the component parts are feldspar, augite, and magnetite 
(or iron ore, which is the black or opaque portion). All these constituents 

* The descriptions here given of Figs. 567 to 572 are condensed from Merrill’s Stones 
for Building and Decoration , pp 34-37. 





636 


THE MATERIALS OF CONSTRUCTION. 


are both hard and tough, and they are so thoroughly bonded that this rock 
resists impact better than granite.* 

In Fig. 569 is shown an oolitic limestone from Kentucky. It is com¬ 
posed of amorphous accretions (the dark portions) about fragmentary nuclei, 
all being cemented together by a crystalline formation of pure calcite (car¬ 
bonate of lime, CaC0 3 , hardness 3).f 

It has been found to weather perfectly, works easily when first quarried, 
hardens on drying out, and is readily carved in most intricate patterns. 

In Fig. 570 we have a silicious sandstone (the Potsdam, from the town 
of Potsdam, N. Y.), that is, a sandstone in which the pure sand (silica) 
grains are also cemented together by a deposit of pure quartz (silica) so that 
the whole is nearly a pure quartz or a quartzite. This is impervious to 
water and is unaffected by all other atmospheric agencies or gases, and hence 
weathers perfectly. It is, of course, very hard to work. 

Fig. 571 is a good illustration of a wholly crystalline limestone or marble. 
In this transformed condition it is without cleavage planes, all traces of its 
original sedimentary formation having disappeared by metamorphism. The 
individual crystals have cleavage planes, shown by the dark stripes, but these 
do not follow any law as to direction. 

Fig. 572 is of a brown (Triassic) sandstone from Connecticut, such as 
has been used so largely for residence fronts through the eastern and middle 
states. The original grains consist of quartz, the clear parts, and feldspar, 
the clouded and banded portions. These are cemented together by carbonate 
of lime, clayey matter, and iron oxide, this last being the black (opaque) 
portions. This kind of sandstone does not weather very well, because of its 
poor (clayey) cementing material. 

The microscopic test, when made by an expert lithologist, will reveal 
more accurately the character and physical composition of a rock than any 
other single test. After such an examination the question of further study 
upon the specimen can be decided more intelligently. 

432. The Absorption Test has for its object to determine the porosity or 
the percentage of water (by weight or by volume, or both) which may be 
absorbed by a dry specimen of the rock. Since some moisture ma,y be 
assumed to be in any rock under normal conditions, it is necessary to first 
dry it for many hours at a temperature above 212° F. It is then weighed 


* This trap-rock, diabase, is an igneous formation, forced up through the Triassic 
sandstones from Nova Scotia to North Carolina, forming great dikes, prominent exam¬ 
ples of which are found in the Palisades of the Hudson, and Mount Holyoke and Mount 
Tom in western Massachusetts. It is much used for paving, foundation walls, and also 
for monuments, when it is known as ‘‘ black granite.” 

f This rock is sedimentary but massive, without seams or cleavage planes, and is 
found widely spread over southern Indiana and northern Kentucky. It has now come 
to be regarded as the leading building-stone of this country. It is commonly known as 
Bedford stone, from the town of Bedford, Ind., where it was first quarried for the 
general market. 



RESULTS OF TESTS ON STONE AND BRICK. 


637 


and placed in clear water for one or more days, depending on the size of the 
specimen and the degree of accuracy desired. Evidently the air imprisoned 
in the rock largely prevents the entrance of the water. An exhaustion of 
this air under a receiver may considerably increase the percentage of absorp¬ 
tion. On removing the specimen from the bath it is wiped dry and weighed 
again. The difference in weight divided by the dry weight gives the per¬ 
centage by weight of moisture absorbed. To find the percentage by volume 
multiply the percentage by weight by the specific gravity of the stone. This 
is much the more significant relation. A series of repeated weighings while 
in the bath will indicate when it has become fully saturated. Table 
XXXVII gives results on a great variety of American building-stones. 

433. The Specific-gravity Test. —The specific gravity, or weight per cubic 
foot, of any building-stone is important and should always be found. For 
hydraulic construction the heavier stones are far more valuable than the 
lighter ones, since the stability of the structure depends on the excess of the 
weight of the stone over that of the same volume of water. Thus, take two 
stones whose specific gravities are respectively 2.8 and 2.0 (175 and 125 
lbs. per cubic foot); their actual weights are as 1.4 to 1, but their relative 
weights in water are as 1.8 to 1. That is, the heavier stone has 80 per cent 
more value than the lighter one in a retaining wall or dam. The solidity of 
a stone, or its freedom from small and microscopic cavities, may also be 
argued from its weight. 

The most ready and accurate means of obtaining the specific gravity is 
by weighing it out of water and then under water; but as there will be some 
absorption when placed in the water, the specimen should first be weighed 
dry, then after soaking in water, as for the absorption test, and finally 
weighed under water. Then the specific gravity can be computed either 
for the wet or for the dry stone as may be desired. 


Thus, let W d — weight dry; 

W„ = “ wet; 

. jr = “ under water. 

IV 


Then we have 


Specific gravity dry = 



w _ w m 

f f w 11 u 


Specific gravity wet = 






(See Table XXXVIII for the specific gravities of the leading varieties of 
American building-stones.) 

434. The Compressive Strength. —The laws governing the compressive 
strength of brittle materials, as stone, were given in Chapter III. It was 
there shown that in order to develop a normal failure in compression it is 
necessary to use specimens having a length in the direction of the stress at 




638 


THE MATERIALS OF CONSTRUCTION. 


m 


7 m 


/7m 


sm 


m 


m 


c w 


_ 

y/ 

-rMp - 

i 

1 

1 

l 

%/ 

7 j> 

a 

A 

/a 


& 

us 

1 

4 

/ \ b// 
( M C 

\ 

NY 

$ 



if h>r 

It: 

N'' 

& 

/ / 
/_ j v 

r F/ 

/ / 
s / / 

7 / 

'OfJ C 

& - 


slI 

'V / 

44 

vv / 

fs .. 





4 r/ 

'/N 

P/J 

/ 





Y/, 

J/rP/i 

/ 

'OP0A 

T/0M 

471 

(1/3 Tl 

W770 

V 




JM 


em 


o mzs m7S 

Fig. 574.— Compression Tests on Four Kinds of Eng¬ 
lish Limestone. {Inst. Civ. Engrs., vol. cvn.) 


AW 


least 1.5 times the least lateral dimension. As a matter of fact, however, 
cubical forms have been almost exclusively used for this purpose, so that in 
order to obtain results which shall be comparable with those which have 
come to be regarded as standard, it is neces¬ 
sary to continue this custom. The relative 
strength of other forms of prisms may be 
found from Fig. 17, p. 32. 

In Chapter XVI the proper methods to 
be employed in making compression tests 
were given, so that these need not be en¬ 
tered upon here. Since all stones which 
would be commonly regarded as suitable for 
building purposes are far stronger than is 
actually required, it follows that the com¬ 
pression test is really of very little conse¬ 
quence, and yet this is in many instances 
the onlv test which is asked for on a new 
building-stone. From Table XL it appears 
that even the lightest sandstones have a 





TT 

[i 

It— 

Y 

i 

l 

1 




i 

i / 
Jh 

---©- 



ll 

r 

l 

I 

L. 

$ 


h 

n 

[Ax o 

i 

1 

l 

-A— 

§ 

Mi 

/ /a 

&y~L r '< 


«// 

ill 

W 

1 

* 

uSl 1 

bn 1 

/ / 
/ / 



bn i 

1 / 

/ / 

/ / 

j 


— ^ - 

* 1 

w 

’ r 

/ 

/ 

/ 


^ / 

^ u 

/ t * t 

n / 

// / / 
Hi a 

1 


P 0 

Wf f 

ill 
/ / 



7Z 

/ / 

/ / 

1 1 



\h// 

M 




» 

m/m 

W/VATi 

-^ 

ll 

wm 


Fig. 575. —Repeated Compression 
Tests on Three Kinds of Scotch 
Granite, {hist. Civ. Engrs., 
vol. cvn.) 


compressive strength of from 4000 to 6000 lbs. per square inch when tested in 
cubical forms. From Fig. 17, p. 32, it appears that the crushing strength 
of stone pillars and columns would be at least 0.8 of these amounts. But the 
greatest load ever placed on stone or brick masonry is commonly not over 
about 10 tons per square foot or 140 lbs. per square inch.* Any stone, 

* This corresponds to the weight of a prism 267 feet high built of masoury weigh 
ing 150 lbs. per cubic foot. 















































m o m 0 m M2 .m M4 .m me' mi 

Fig. 576.—Compression Tests on Free (Sand) Stone Cubes. (Gillmore.) 


RESULTS OF TESTS 


ON STONE AND BRICK. 


639 



































































640 


THE MATERIALS OF CONSTRUCTION. 


TABLE XL.—PHYSICAL PROPERTIES OF BUILDIXG-STONES. 


Condensed from Merrill’s Stones for Building and Decoration. 


Kind of Stone. 

Locality. 

Position. 

Strength per 

Square Inch. 

Specific Gravity. 

o 

2 

o 

5 

a 

r 

4 -> 

Bo 

£* 

Percentage of 

Absorption 

by Weight. 

Number of Speci¬ 

mens averaged. 

1. Granite 

Grape Creek, Brownsville, Law-' 
son, Platte Canon, Cotopaxi, 
Monarch, Gunnison — Colo. \ 


j Bed 
( Edge 

lbs. 

15,531 

18,536 

2.68 

lbs. 

187.3 

1.1 

8 

2. Granite 

New London, Millstone Point,' 
Mystic River, Stony Creek— 
Conn. Vinalhaven, Fox Isl¬ 
and, Dyer’s Island, City Point, 
Dix Island, Jonesboro, Spruce- 
head, Hewitt’s Island, Hurri¬ 
cane Island— Maine. Huron 
Island— Mich. 

> 

► 

Bed 

16,200 

2.65 

166.0 

0.4 

20 

3. Granite 

East Saint Cloud, Saint Cloud,) 
Watab, Sauk Iiapids, Beaver : 
Bay — Minn. J 


(Bed 
( Edge 

24.464 

24.464 

2.65 

165.8 

0.5 

7 

4. Granite 

Cape Ann, Rockport, Quincy—) 
Mass. \ 


Bed 

16,079 

2.67 

167.0 

0.7 

4 

5. Granite 

Fall River, Mouson — Mass .' 
Keene — N. II . Tarry town, 
Morrisania, Staten Island, 
North River, Madison Ave¬ 
nue, Chaumont Bay-— N. Y. 
Westerly — R. I Richmond 
— Va. 

> 

Bed 

15,570 

2.69 

168.0 

0.4 

14 

6. Granite 

New Haven — Conn. Duluth,' 
Taylor’s Falls, Beaver Bay— 
Minn. Jersey City Heights, 
Pompton— N. J. Goose Creek 
(Loudoun County)— Va. 


(Bed 
( Edge 

21,272 

20,740 

2.82 

176.2 

0.3 

6 

7. Limestone 
(oblitic) 

Putnamville. Greensburgh, Saint) 
Paul, Harrison County, Mount - 
Vernon, Bloomington— Ind. ) 


Bed 

14,054 

... 

156.2 

1.4 

6 

8. Limestone 

Spencer, Ellettsville, Bedford,) 
Salem — Ind. j 


Bed 

9,297 

.... 

145.9 

3.6 

8 

9. Limestone 

Bardstown — Ky. 


jBed 
(Edge 

i6,250 
15 000 

2.67 

166.9 

1.2 

1 

10. Limestone 

Lee — Mass. 


j Bed 
l Edge 

22,323 

21,728 












11. Limestone 

Frontenac, Stillwater, Winona,) 
Red Wing, Kasota, Mautor- - 
ville — Minn. ^ 


(Bed 
) Edge 

16.320 

16,643 

2.52 

157.3 

3.1 

7 

12. Limestone 

Glens Falls, Lake Champlain,' 
Canajoharie, Kingston, Garri¬ 
son’s Station, Williamsville — 
N. Y 

- 

(Bed 

(Edge 

16,971 

15,533 

2.58 

168.1 

• • • • 

6 




































RESULTS OF TESTS OF STONE AND BRICK. 


641 


PHYSICAL PROPERTIES OF BUILDING-STONES— Continued. 





l 

! 

o 

!3 


i 

■ m 

Kind of Stone. 

Locality. 

G 

- O 

a) a 

a: p 

^ i 

> I 

cS 

s- 

0 

o 

3 

o 

s_ 

© 

a 

c =0 
©.2.= 
bC 

■*-> ~ ► 

£% 

O © 

. > 



o 

-*-> 

hn 2 

a ~ 

s 

*3 

h -g 
.Sfo 

c o < 

© 

JZ 'S> 

£ 0 



cfi 

O 

t-C/2 

C/2 

© 

a 

cc 

A U-t 
* 


5 | 




lbs. 


lbs. 



IB. Limestone ’ 

Montgomery County— Pa. 

j Bed 
(Edge 

13,112 

11,055 




4 

(marble) 






14. Limestone 

Dorset— Vermont. 

(Bed 

10,506 

2.64 

164.7 

• • • » 

2 

(marble) 


1 Edge 

8,670: 

2.68,167.8 

. • . . 

1 

15. Limestone 

[taly. 

Bed 

12,156 

2.69 

168.2 


1 

(marble) 





16. Sandstone 

Buckhorn (Larimer Co.), Trini- 'j 








dad (Las Animas Co.), Mani- 
tou (El Paso Co.), Ralston, 
Left Hand, Saint Vairus, Fort } 

(Bed 

1 

11,141 

2 13 

132.9 

6.6 

9 


Collins (Larimer Co.), Stout 
(Larimer Co )— Colo. Thistle 
— Utah 

) Edge 

12,434 





17. Sandstone 

Coal Creek, Oak Creek (Fremont 1 








Co.),Gunnison (Gunnison Co.), 
Manitou (El Paso Co.), La 1 

(Bed 

5,481 

2.12 

133.0 

13.8 

9 


Porte (Larimer Co.), Brand- 

(Edge 

4,941 



ford (Fremont Co.) — Colo. 







18. Sandstone 

Middletown, Portland — Conn.) 







East Long Meadow — Mass. > 
Marquette — Mich. ) 

Bed 

(Bed 
} Edge 

6,639 

2.27 

142.2 

3.5 

3 


19. Sandstone 

Hinckley, Fort Snelling — Minn. 

16,625 

18,750 

2.38 

139.0 

6.0 

2 

20. Sandstone 

Dresbach, Jordan, Fond du Lac,) 

(Bed 

5,789 

1.99 

124.4 

9.9 

a 


Dakota — Minn. ( 

{Edge 

4,102 


21. Sandstone 

Taylors’ Falls, Kasota, Froute-) 

( Bed 

7,483 

2.42 

142.4 

5.9 

Q 

nac— Minn. ( 

(Edge 

9,725 


22. Sandstone 

Haverstraw, Hudson River, Al-) 

(Bed 

8,925 

2.78 

142.2 

2 6 

2 


bion — N. Y. ( 

) Edge 

7,68? 


Medina — N. Y. 

(Bed 

17.500 2.42 

150.8 

1.6 

2 

23. Sandstone 

^ Edge 

14,812 

,2.39 

149.3 

2.0 

1 

24. Sandstone 

Vermillion — Ohio. 

j Bed 
( Edge 

, 7.84C 
6,87f 

2.16 

135.0 

5.2 

5 

1 

25. Sandstone 

Seneca — Ohio. 

( Bed 
\ Edge 

9,681 

10,50( 

J2.3f 

149.3 

3.1 

1 

26. Sandstone 

Cleveland — Ohio. 

(Bed 
l Edge 

6,80( 

7,91( 

] 2.24 

1140.( 

) 2.8 

1 

27. Sandstone 

Marblehead — Ohio. 

j Bed 
( Edge 

! 7,93 r 
6,85( 

O Ql 

■j /w • O 

144/ 

t 5.2 

1 

28. Sandstone 

North Amherst — Ohio. 

( Bed 
\ Edge 

6,215 
5i 5,45( 

^ 2.1( 

, 133/ 
5 135/ 

5.2 

2 

1 

29. Sandstone 

Berea — Ohio. 

Bed 

, 9,231 

32.i: 

3133. ( 

) 5.5 

2 






































































642 


THE MATERIALS OF CONSTRUCTION. 


therefore, having a crushing strength of 3000 lbs. per square inch is quite 
strong enough for all ordinary building purposes, the strength of masonry 
being measured by the strength of the mortar used. N hile there is no ob¬ 
jection to greater strength, and while strength may be some evidence of 
weathering resistance, yet it cannot be said that one stone is better than 
another for building purposes simply because its crushing strength is 
20,000 lbs. per square inch, whereas the strength of the other is only 
5000 lbs. per square inch. In the opinion of the author this difference 
of strength, taken alone, has no significance and should be given no 
weight. 



Fig. 577.—Elastic Propeilies of Various Slones under Compressive Stress. ( Wat. Ars. 

Rep. 1894.) 

435. The Elastic Properties and Crushing Strength of Building-stones. 

'—Limestones and granites are nearly perfectly elastic for all working loads, 
while sandstone takes permanent sets for the smallest loads. These qualities 
are well illustrated in Fig. 574 for limestone, Fig. 575 for granite, and Fig. 

576 for sandstone. These figures show that some permanent set accompanies 
all loads even on the limestones and granites, but these are extremely small 
as compared to those on the sandstone. Similar results appear also on Figs. 

577 to 583. 

In all these stress-diagrams the modulus of elasticity may be taken off by 
extending a tangent to the curves at the origin till it intersects the vertical 
line marking a deformation of 0.001 of the length. The corresponding load 
in pounds per square inch, taken from the stress argument, when multiplied 




















RESULTS OF TESTS ON STONE AND BRICK. 


m 


"by 1000 gives the modulus of elasticity in compression. Bauschinger has 
shown that this is practically the same as that obtained from bending tests, 
and hence it may be used for computing the deflection of stone beams. The 
moduli of elasticity given in Table XLI are those found in cross-bending 
on the first loading. Bauschinger gives them also in every case for 
tension and for compression; but these are not reproduced here, as they 
are practically the same as in cross-bending. By comparing the results 
in this table there seems to be no general or fixed relation between the 
various kinds of strength of stone. As these tests were made with the 
greatest care and precision, this table must be accepted as conclusive on this 
point. 

TABLE XLI.—PROPERTIES OF THE BUILDING-STONES OF BAVARIA. 

(Bauschinger’s Communications, vol. x, 1884.) 

Strengths given in Pounds per Square Inch. 


Kind of Stone. 

Specific Gravity. 

Weight per 

Cubic Foot. 

Cross-bending. 

Compressive Strength. 

Tensile Strength. 

Shearing 

Strength. 

Modulus 

of 

Elasticity 

Mod¬ 
ulus of 
Rup¬ 
ture. 

Perpen¬ 
dicular 
to Bed. 

Parallel 
to Bed. 

Parallel 
to Bed 
after 25 
Freez 
ings. 

Perpen¬ 
dicular 
to Bed. 

Par¬ 

allel 

to 

Bed. 

Granite. 

2.65 

165.4 

2,986,000 

1,365 

19,200 

18,910 

21,470 

619 

1,379 

142 

4k 

2.66 

166 

1,621,000 

1,194 

19,200 

20,050 

20,480 

683 

1,450 

853 

Triassic limestone. 

2.48 

154.8 

6,420,000 

882 

8,130 

8,320 

6,810 

583 

555 

384 

Jurassic limestone (marble) 

2 23 

139.2 

.... 


11,110 

7,410 

12,290 

448 

739 

540 

4 4 44 14 

2.08 

129.8 

4,906,000 

462 

4,664 

8,760 

3.313 

213 

498 

299 

Oolitic limestone 

2.72 

169.7 


1,792 

19,340 

20,620 

18,770 

910 

1,479 

1,138 

Tuffa stone.. 

1.80 

112.3 


469 

1,195 

2,545 

2,076 

227 

227 

'213 

Variegated sandstone. 

2.06 

128.5 

426,600 

469 

7,420 

6,010 

6,730 

107 

569 

355 

44 4 4 

2.20 

137.3 

867,400 

718 

9,040 

7,790 

7,910 

199 

512 

313 

44 4 4 

2.28 

142.3 

1,340,000 

1,109 

12,930 

13,410 

11.520 

576 

910 

540 

44 4 4 

2.00 

124.8 

341,300 

341 

6,160 

6,100 

4,877 

128 

455 

427 

Carboniferous sandstone — 

2.20 

137.3 

910,000 

483 

7,636 

8,390 

5,986 

341 

640 

284 

w limestone ... 

2.23 

139.1 

334,200 

441 

6,681 

6,670 

5,900 

213 

583 

469 

Slaty sandstone. 

1.82 

113.6 

512,000 

249 

3,071 

2,247 

2,161 

9S 

370 

242 

4 4 44 

1.92 

119.8 

270,200 

135 

3,029 

2,659 

4,252 

67 

242 

185 

Green sandstone. 

2.15 

134.2 

583,000 

156 

4,707 

4.308 

4,038 

94 

341 

327 


2.60 

162.3 

568,800 

597 

13,510 

14,500 


327 

668 

370 

44 44 

2.73 

170.4 

2,687,000 

967 

28,860 

17,490 


512 

995 

768 

Quartz conglomerate. 

2.29 

142.9 

1,763,000 

654 

5,546 

4,408 

3,270 

242 

.... 

.... 


In Table XLII we have given, in addition to the usual compressive 
strength, the modulus of elasticity in compression, the shearing strength, the 
ratio of lateral to longitudinal deformation from stress (Poisson’s ratio, see 
Art. 5, p. 5), and the coefficient of expansion. This last property of stone 
the author has not found elsewhere, and as it is a very important one, the 
table has great value for this alone. The coefficient of expansion of iron and 
steel is about 0.00000G5 (varying from 0.0000050 to 0.0000070), while that 
of stone and cement, as shown by this table, varies from about 0.0000020 to 
0.00000G0. Iron or steel embedded in stone masonry, therefore, would have 
a very small relative expansion and contraction from temperature. It will 
be noticed that Poisson’s ratio varies from } to so that the value 




















































644 


THE MATERIALS OF CONSTRUCTION. 



Fig. 578. —Elastic Properties of Various Stones under Compressive Stress. {Wat. Ars. 

Rep. 1894.) 



Fig. 579.— Elastic Properties of Various Stones under Compressive Stress. {Wat. Ars. 

Rep. 1894.) 


































RESULTS OF TESTS ON STONE AND BRICK. 


645 


which is commonly assumed for metals, would also serve very well for 
stone. 


TABLE XLII. —TESTS OF AMERICAN BUILDING-STONE MADE AT TIIE 

WATERTOWN ARSENAL. 

(Rep. 1894.) 


Name of Stone. 

Veight 

per 

Cubic 

Foot. 

Compression Tests. 

Ratio of 
Lateral 
Expan¬ 
sion to 
Longi¬ 
tudinal 
Compres¬ 
sion.* 

Shearing 

Strength. 

Coefficient of 
Expansion 
in Water. 

Strength 
in Pounds 
per Square 
Inch. 

Modulus of 
Elasticity for 
Working 
Loads. 


Pounds 




Pounds. 


Braudford granite (Conn.)... 

162.0 

15,707 

8,333,300 

0.250 

1,833 

.00000398 

Milford granite (Mass.). 

162.5 

23,775 

6,663,000 

0.172 

2,554 

.00000418 

a i « a 






00000415 

Troy granite (N. H.). 

164.7 

26,174 

4,545,400 

0.196 

2,214 

.00000337 

Milford pink granite (Mass.). 

161.9 

18,988 

5.128,000 

• • • • 

1,825 


Pigeon Hill granite (Mass.).. 

161.5 

19,670 

6,666,700 

* • • • 

1,550 


Creole marble (Georgia). .. 

170.0 

13,466 

6,896,500 

0.345 

1,369 


Cherokee marble (Georgia). 

167.8 

12,618 

9,090,900 

0.270 

1,237 

.00000441 

Etowah marble (Georgia)... 

169 8 

14,052 

7,843,100 

0.278 

1,411 


Kennesaw marble (Georgia).. 

168.1 

9,562 

7,547,100 

0.256 

1,242 


Bee marble (Mass.). 




_ 


.00000454 

Marble Hill marble (Georgia) 

168.6 

11,505 

9,090,900 

0.294 

1,332 

.00000194 

Tuckahoe marble (N. Y.). .. . 

178.0 

16,203 

13,563,200 

0.222 

1,490 

.00000441 

Mt. Vernon limestone (Ky.).. 

139.1 

7,647 

3,200,200 

0.250 

1,705 

.00000464 

Oolitic limestone (Ind.). 






.00000437 

Hortli River bluestone (N.Y.) 

• • • • 

22,947 

5,268,800 

• • • • 

• • • • 


Monson slate (Maine). ...... 






.00000519 

Cooper sandstone (Oregon) .. 

159.8 

15,163 

2,816,900 

0.091 

1,831 

.00000177 

Sandstone, Cromwell (Couu.) 

.... 

10,780 

• «.•••• 

... 

• • • • 


Maynard sandstone (Mass.)... 

133,5 

9,880 

1,941,700 

0.333 

1,204 

.00000567 

Kibble sandstone (Mass). .. 

133 4 

10,363 

1,834,900 

0.300 

1,150 

.00000577 

Worcester sandstone (Mass).. 

136.6 

9,762 

2,439,000 

0.227 

1,242 

.00000517 

Botomac sandstone (Md.).... 






.00000500 

Olympia sandstone (Oregon). 

• • • • 

12,665 


• • • 

o • • • 

.00000320 

Cllmr.kflnut, sMiulstonp(AVash .) 


11,389 



1,352 


Dyckerhoif Portland cement, 





neat. 






.00000578 



• 






* See Art. 5, p. 5. 


436. Resistance to Abrasion.— When a stone is strong and tough enough 
to resist the chipping action of the iron horseshoes and wagon-tires upon it 
when used as a paving material, and when it weathers perfectly, its life is 
measured by its resistance to the abrading action of the traffic. Prof. 
Bauschinger very fully investigated this subject, and his results are recorded 
in volume xi of his Communications (1884). We here find some 900 tests of 
paving materials, most of which are summarized by averages in Table XLIII. 
His apparatus is shown in Fig. 585, which is modelled after a similar machine 
shown at the world’s fair held in Paris in 1878. The cut as here shown is 
to a scale of one-half inch to the foot, so that the diameter of the revolving 
table was about five feet. Any given specimen was held to a fixed position 




















































646 


TEE MATERIALS OF CONSTRUCTION. 


on the plate, two specimens being tested at one time. The specimens were 
all dressed to 4 inches (10 cm.) square, and they were weighted with 30 kilo¬ 
grams, or about 4 lbs., per square inch. Tests were made both with and 



Fig. 580.—Compression Tests on Four Kinds of English Dolomite. (Inst. Civ. Engrs., 

vol. cvn.) 



Fig. o81. Compression lests on Three Kinds of Oolitic Limestone. (Inst. Civ. Engrs. y 

vol. cvn.) 


without the use of water, but mostly without, as shown in the table Fine 
emer\ (^No. 3) vas fed to the plate by hand at the rate of 20 grams for every 
10 revolutions, the old emery being at the same time brushed off. Two 
attendants constantly kept the emery in the path of the specimen. The 




































































RESULTS OF TESTS ON STONE AND BRICK. 


647 



Fig. 582.—Compression Tests on Three Kinds of English Sandstone. {Inst. Civ. 

Engrs., vol. evil.) 



Fig. 583._Elastic Properties of Various Stones under Compressive Stress. {Wat. Ars. 

Rep. 1894.) 































































648 


THE MATERIALS OF CONSTRUCTION. 


speed was 20 revolutions per minute, and 200 revolutions completed a test, 
so that the test lasted but 10 min. The different specimens were set at 
different distances from the centre, so as to wear the cast-iron table evenly, 
and the results were all reduced to a standard radius (distance from the 
centre) of 49 cm. (19.5 in.). Elaborate preliminary studies were made to 



Fig. 584.—Elastic Properties of Various Stones under Compressive Stress. (Wat. Ars.. 

Rep. 1894.) 

determine the best rate of feeding emery, best size of grain, best weighting* 
of specimen, and the law of wear as the distance out from the centre 
varied. Some of the results of these preliminary tests are shown in 
Figs. 58G and 587. The average results as recorded in Table XLIIX 
indicate: 

1. That the wet grinding was about twice as effective as the dry grinding;, 
the exact average ratios being given in the last column of the table for each 
species of stone.* 

2. There is no fixed relation between crushing strength and abrasive 
resistance. 

3. The limestones wear about five times and the sandstones about four 
times as fast as the granites, porphyries, and basalts. 


* These ratios have been taken out from the wet and dry tests on identical material 
and therefore are not the ratios of the two general average results in the previous 
column. 



























RESULTS OF TESTS ON STONE AND BRICK. 


649 



Fig. 585.—Bauschinger’s Apparatus for Determining Resistance to Abrasion of Paving 

Material. 



Fig. 586.—Showing the Relation between the Abrasion, Pressure, and Energy used. 

(Bauschinger.) 

































































































































































650 


THE MATERIALS OF CONSTRUCTION. 


TABLE XLIII.—AVERAGE RESULTS OF BAUSCHINGER’S ABRASION TESTS OF 

PAVING MATERIAL. 

( Communications , vol. xi, 1884.) 

Four-inch cubes of the material were pressed on an iron plate with a weight of four 
pounds per square inch, and 20 grams of emery fed every 10 revolutions. Results 
obtained for 200 revolutions at a radius of 19.5 inches. 


Kind of Material. 


Average 
Average Weight 
Specific per Cubic 
Gravity. Foot in 
Pounds. 


Average 
Com¬ 
pressive 
Strength 
in Pounds 
per 

Square 

Inch. 


Num- i 
her of I 
Results 
Aver¬ 
aged. | 


How 
ground- 
Dry or 
Wet. 


Average 
Loss of 
Volume 
in Cuitic 
Inches. 


Ratio: 
Loss wet 
Loss dry’ 


Granite. 

Syenite...., 

Diorite. 

Hornblende 
Porphyry . 


2.63 

2.27 

2.87 

2.82 

2.57 


Basalt.... 

Gneiss.. .. 
Quartz.. . 

Clay-slate. 

Breccia .. 

Limestone 


3.01 

2.61 

2.63 

2.72 

2.61 

2.87 


Sandstone 


2.48 


Brick and tile. 

Artificial stone made with 
Portland cement. 

Asphalt paving. 


2.98 

2.36 

2.33 


164 

142 

180 

176 

161 

188 

163 

165 

170 

163 

180 

155 

187 

148 

146 


22,400 

18,780 

26,200 

21,900 

24.500 

34,200 

23,000 

17.500 

26,000 

22,600 

20.500 

17.600 


j 

i 

I 

i 

\ 


92 

8 

24 

1 

18 

2 

2 


( 93 
\ 8 
j 86 
\ 4 
4 
9 

) 8 
10 
f 163 
\ 32 
j 44 
( 38 
f 105 
I 34 
j 20 


dry 

wet 

dry 

wet 

dry 

wet 

dry 

dry 

wet 

dry 

wet 

dry 

wet 

dry 

wet 

dry 

dry 

wet 

dry 

wet 

dry 

wet 

dry 

wet 

dry 

wet 


0.24 

0.46 

0.28 

0.82 

0.27 

0.68 

0.19 

0.20 

0.24 

0.19 

0.47 

0.21 

0.19 

0.16 

0.35 

0.20 

1.10 

1.41 

0.81 

0.64 

0.38 

0.75 

0.51 

1.82 

0.61 

1.62 


j- 1.72 
j- 1.90 
j. 1.90 

j j- 1.72 

12.31 

• • • • 

• • • • 

j- 2.76 

• • • • 

j-1.60 

i 225 

| 2.50 
| 3 20 
| 2.68 



Fig. 587. —Showing the Relation between the Abrasion, the Emery used, and the 

Pressure exerted. (Bauschiuger.) 



































































RESULTS OF TESTS ON STONE AND BRICK. 


651 


4. The clay-slate shows the best results in abrasion, but only a few speci¬ 
mens were tested. 

5. The brick and tile wear about twice as fast and the cement composi¬ 
tions about three times as fast as the primitive rocks. 

6. The resistance of asphalt paving to abrasion falls between the cement 
mixtures and sandstone. 




Fig. 589. 


Fig. 588.—Elastic Properties of Common Brick used in Pier Tests. The average crush¬ 
ing strength of these three grades of brick, crushed endwise, was 14,000, 10,500, 
and 7500 lbs. per square inch respectively. ( Wat. Ars. Rep. 1885, p. 1138.) 

Fig. 589.—Showing Method of Failure of Brick Piers. (Wat. Ars. Rep. 1883.) 


BRICK. 

437. The Strength and Elastic Properties of single bricx are of relatively 
small importance unless the mortar bond has nearly as great strength. As 
this is never the case except a rich Portland-cement mortar be used, it 
follows that in ordinary brick masonry the strength and rigidity of the brick 
used is of small importance provided any reasonably firm brick be employed. 
Thus in Fig. 588 we have three stress-diagrams of compression tests of single 
brick, showing moduli of elasticity from 2,000,000 to 4,000,000, and an 





























































652 THE MATERIALS OF CONSTRUCTION. 



\m<? 








































































































RESULTS OF TESTS ON STONE AND BRICK. 


653 


ultimate crushing strength from 8,000 to 14,000 lbs. per square inch. In 
I ig. 590 are shown the stress-diagrams of tests on columns from 6 to 10 feet 
high built from the strongest of the brick tested in Fig. 588, but with 



Fig. 591.—Strength of Columns of Single Hard-burned Eastern Face-brick laid flatwise 
one upon another with Plaster-of-paris Joints. Each result the mean of two tests. 
Crushing losds given in pounds per square inch. {Rep. Wat. Ars. 1894, p. 440.) 


7 





1- 





% - 






7 . 



.a 











i/ 

/ / 



4 

0\V,. 

y 

) 

$ 

4 

% 






i 

q\y 

yd 


Sr 

{ 

% 




t 




A 



j°y 

/ 



a\V 

m 

& 

* 

$ 

Wn 

0/ 

,/ r' X 

S' 



4 

\V 

/ p 

L-A 

f 

k 

fi 



* , 

Wj 

by 

f 

in_ 



ft? 



< 

& 

f 


# 

if 



1/ 

h § 

V 

/ 


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$ 

1 mt 

f 


h 

•# 



f, i 
jp< / 





s 



w 

, w 

1 



r,® 




fii 

l! 1 




? 1 

0 1 




// 

* 



j i 

<p t 

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& i 




' '1 
> 66 

0 fi 

0 0 

00 ] 

he 

A/ / 

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ft t 

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ST 

O Ft\ 

h 

T/ i 

7/Z 


_J 


m 




0 \00J J02 M 0 .00/ .002 .003 0 .00/ .002 .003 0 .00/ 2/02 J%73.004 
Fig. 592.—Strength of Brick Piers with Roseudale-cement-mortar Joints, 1 C. : 2 S. 

(Wat. Ars. Rep. 1883.) 


various kinds of mortar. When lime-mortar (1 lime to 3 sand) was used 
at ages from 18 months to 2 years, the modulus of elasticity for the column 
as a whole varied for the first loads from 250,000 to 750,000, and the ulti¬ 
mate strength from 750 to 1300 lbs. per square inch. The method of failure 














































654 


THE MATERIALS OF CONSTRUCTION. 


of all these columns is fairly indicated in "Fig. 589. They always split 
longitudinally and spread apart, thus showing that the tensile strength of 
the brick is really a very important quality. 



When Rosendale (natural) cement mortar (1 C. : 2 S.) was used the 
modulus of elasticity was raised to about 2,000,000, and the ultimate strength 
to 2000 lbs. per square inch. 

When Portland-cement mortar (1 C. : 2 S.) was used the modulus of 
elasticity of the column was raised 3,000,000, and the strength to 2500 lbs. 
per square Inch. 

The effect of adding one part of Rosendale or of Portland cement to two 
parts of lime and three parts of sand is shown by two diagrams on Fig. 590. 





























































RESULTS OF TESTS OF STONE AND BRICK. 


655 





































656 


TEE MATERIALS OF CONSTRUCTION. 



Fig. 595. —Strength of Common-brick Piers with Rosendale-cement-mortar Joints, 

1 C. : 2 S. (Wat. Ars . Rep. 1883.) 



Fig. 596. —Strength of Common-brick Piers with Rosendale-cement-mortar Joints, 

1 C. : 2 S. (Wat. Ars. Rep. 1883.) 


























































RESULTS OF TESTS OF STONE AND BRICK. 


65? 



Fig. 597.—Strength of Common-brick Piers with Roseudale-cement-mortar Joints, 

1 C. : 2 S. {Wat. Ars. Rep. 1883.) 



Fig 598 _Strength of Face-brick Piers with Portland-cemeut- and Lime-mortar JointSi 

{Wat. Ars. Rep. 1883.) 







































































658 


THE MATERIALS OF CONSTRUCTION, 


The ultimate strength is raised to 1050 lbs. with the Rosendale, and to 1450 
lbs. per square inch when using the Portland cement, while the modulus of 
elasticity is also greatly increased, especially under the higher loads. 



The effect of height, as related to breadth, on the crushing strength of 
brick is shown in Fig. 591, where results are given for bricks crushed flat¬ 
wise in columns of one, two, three, four, and five bricks high, with plaster- 
of-paris beds. This curve is quite similar to that in Fig. 17, p. 32. 

The remaining diagrams, given in Figs. 592 to 000, showing the strength 











































RESULTS OF TESTS ON STONE AND BRICK. 65li 

of brick columns are thought to be self-explanatory and therefore need no 
further comment here. The original publications, furthermore, are generally 
accessible in this country. 



Table XLIV contains a record of tests on some of the best building 
brick, as made by the hydraulic dry-press method, the tests in crushing 
having been made upon the bricks flatwise. This gives results about 25 per 
cent greater than if the tests were made on cubical forms, and 40 per cent 
greater than if the brick had been crushed edgewise, as was the case with 
the paving-brick tests on which are recorded in Table XLV. 





































THE MATERIALS OF CONSTRUCTION. 


66d 

TABLE XLIY. —COMPARISON OF TRANSVERSE AND CRUSHING TESTS 

OF BRICK. 


(From Watertown Arsenal Tests for 18S4.) 




Modulus of 



Trans¬ 

verse 

Test 

No. 

Kind of Brick. 

Rupture in 
Transverse 
Tests, 
Pounds per 
Square Inch. 

3 Wl 

Mean Crushing 
Strength Flat¬ 
wise, 

Pounds per 
Square Inch. 

Ratio: 
Crushing 
Transverse' 



f ~ 2 6/i 2 ‘ 



212 


754 

10,350 

13.8 

213 

From 

Hydraulic Pressed Brick Co., St. Louis 

833 

17,698 

21.2 

214 

215 

829 

868 

8,495 

10,483 

10.2 

12.1 

216 


604 

5,573 

9.2 

223 

From 

455 

5,596 

12.3 

224 

Hydraulic Pressed Brick Co., Chicago 

308 

3,271 

10.6 

226 

From 

Hydraulic Pressed Brick Co., Omaha 

1,244 

13,506 

10.9 


From 




225 

Northern Hydraulic Pressed Brick Co., 

455 

6,583 

14.4 


Minneapolis 




206 


936 

12,823 

13.7 

207 

From 

Eastern Hydraulic Pressed Brick Co., 
Philadelphia 

1,232 

13,052 

10.6 

208 

209 

210 

1,066 

756 

1,038 

15,633 

12,196 

12,4^5 

14.6 

16.1 

11.9 

211 


974 

12,866 

13.2 

217 


785 

8,848 

11.3 

218 

From 

1,043 

11,867 

11.4 

219 

741 

7,778 

10.5 

220 

Philadelphia and Boston Face-brick Co., 

568 

3,093 

5.4 

221 

Boston 

858 

8,217 

9.6 

222 

1 


358 

2,686 

7.5 


438. Results of Tests of Paving-brick.—Table XLY contains the results 
of tests made by the author on paving-brick in accordance with the methods 
he has established and described in Chap. XXII. The brick intended for 
the cross-breaking and for the crushing tests are ground first on one flat side 
to obtain a true plane of reference, and then on the opposite edges to true 
parallel planes. This grinding is done for him at a regular stone (marble) 
works, and there seems to be little difficulty in obtaining satisfactory 
results. The knife-edge bearings used in the cross-breaking tests are some¬ 
what rounded, but are not cushioned. 

The ends of brick which have been broken across are then used for the 
crushing test. The crushing force is applied edgewise, using ordinary tar- 
board as a cushioning material. Plain steel surfaces are better if they are 
perfectly true. One of the bearings should be adjustable or have a ball-and- 
socket support. The specimen must also be placed exactly in the axis of the 



















































RESULTS OF TESTS ON STONE AND BRICK. 


661 


TABLE XLV.—TESTS OF PAVING-BRICK MADE BY THE AUTHOR. 

(Private Records.) 


Mark. 

Number of 
Tests 
Averaged. 

Modulus of 
Rupture in 
Cross breaking 
Edgewise in 
Pounds per 
Square Inch. 

_ Siof 

J ~ 2 blA' 

Crushing 
Strength 
Edgewise in 
Pounds per 
Square Inch 

A 

12 

1,369 

4,885 

B 

5 

1,495 

4,974 

C 

6 

2.808 

9,890 

D 

3 

3,032 

16,140 

E 

4 

2,620 

12,330 

F 

3 

2,734 

15,155 

G 

3 

2,335 

12,040 

H 

3 

2,335 

17,500 

I 

3 

2,825 

17,480 

J 

3 

2,100 

13,150 

K 

5 

2,570 

20,420 

L 

5 

2,152 

15,530 

M 

18 

2,401 

13,366 

N 

6 

2,635 

15,360 

O 

6 

2,208 

13,300 

P 

5 

2,674 

16,830 

Q 

6 

2,320 

14,420 

R 

4 

3,110 

20,802 

s 

4 

1,780 

11,037 

T 

5 

2,930 

13,260 

U 

3 

2,570 

10,400 

V 

5 

2,640 

7,830 


Impact Test. (See Art. 337, p. 457.) 


Loss of 
Weight of 
Brick, 
Per Cent. 

Loss of 
Weight of 
Granite 
Blocks, 
Per Cent. 

Ratio: 

Loss of brick 
Loss of granite 

Absorption 

Test.. 

Percentage 
of Water 
by Weight. 

9.84 

2.34 

4.2 

5.32 

13.82 

2.78 

' 4.97 

4.1 

12.15 

2.5 

4.85 

0.64 

16.42 

3.6 

4.56 

1.36 

13.98 

3.6 

3.88 

3.40 

14.34 

3.6 

3.98 

1.12 

26.54 

3.6 

7.37 

0.87 

19.17 

3.6 

5.32 

0.64 

11.04 

3.6 

3.07 

1.12 

18.38 

3.6 

5.11 

0.33 

26.67 

3.38 

7.89 

0.55 

13.0 

3.2 

4.06 

2.20 

15.7 

1.8 

8.7 

0.79 

16 3 

4.1 

4.0 

2.79 

15.3 

5.0 

3.1 

2.92 

8.65 

2.45 

3.55 

1,29 

14.53 

3.41 

4.26 

0.67 

19.5 

2.5 

7.8 

0.5 

13.48 

3.03 

4.45 

6.61 

11.37 

3.89 

2.92 

3.03 

15.1 

2.21 

6.83 

2.2 

34.1 

2.21 

15.4 

1.1 


machine. Failure should come suddenly with a loud report, with little or 
no previous spalling of the specimen. 

The impact tests were made in a tumbler, or rattler, made up by lining 
an oil-barrel with steel strips and mounting it on trunnions. Standard 
Missouri granite blocks, rectangular in form, and weighing about the same 
as a paving-brick (6 lbs.) are obtained in quantities, specially prepared for 
these tests. There were always five of these, freshly cut (not sawed), put in 
the rattler along with the brick, and the rattler run at 30 to 40 revolutions 
per minute for 15 to 30 minutes. The loss in weight of the brick is then 
found as compared with the loss in weight of the granite blocks. It has 
been customary to add from 5 to 10 cast-iron bricks, having rounded edges, 
specially cast for the purpose, these also weighing 6 pounds each. Evidently 
such a test is in no sense an abrasion test, but strictly a test for shock resist¬ 
ance, or for resistance to impact. 

The absorption test has been made by drying 24 hours on top of boilers 
and then soaking 24 hours. While these intervals are not long enough to 
give absolute results, they serve very well for commercial purposes. The 
bricks which have been through the rattler are used for this test, as their 
glazed surfaces are then largely removed. 

























062 


THE MATERIALS OF CONSTRUCTION. 


TABLE XLYI.—TESTS OF BUILDING-BRICK AT THE 
WATERTOWN ARSENAL. 

{Rep. 1894.) 


Description of Brick. 


Hydraulic Press Brick Co. 
—St. Louis, Mo. 

Medium red. 

Dark red. 

Paving stock. 

Paving stock .. 

No. 6 stock, dark red. 

No. 10 stock, dark red . 

No. 500 stock, buff, speckled .. 
No. 503 stock, light, chocolate.. 
No 504 stock, light choco ) 
late with dark speckles ) '' 
No. 509 stock, dark buff ^ 
with darker speckles f ‘ ’ 

No. 510 stock, buff with ) 
dark speckles f ‘* 

No. 511 stock, light buff. 

Brown. . 


CirrcAGo Hydraulic Pres 
Brick Co.—Chicago, III. 

Brown. 

Red. 

Red. . 


Omaha Hydraulic Pre 
Brick Co.—Omaha, Neb. 

Shade No. 5. 

Shade No. 7. 

Shade No. 6. 


Brick Co.—Minneapolis 
Minn. 

Dark red. 

Dark red . 

Brooke Terra Cotta Co.— 
Lazearville, W. Ya. 

No. 4, dark buff. 

No. 5, medium dark buff .... 
No. 10, light buff. 

Findlay Hydraulic Pres: 
Brick Co.—Findlay, Ohio. 

No. 12, dark red. 

No. 18, dark red. 

No. 14, dark red. 


Compression 

Test. 

Cross¬ 
breaking 
Strength 
in Pounds 
per 

Square 

Inch. 

3 Wl 
f ~2‘ bh" 1 

Shearing 
Strength 
in Pounds 
per 

Square 

Inch. 

Percentage 
of Absorption 

Direction 

of 

Loading. 

Crushing 
Strength 
in Pounds 
per 

Square 

Inch. 

By 

Weight. 

By 

Volume 

Flatwise 

5,266 

• • • • 

• • • • 

18.0 

31.5 

< < 

10,284 

754 




t ( 

17,558 

• • • • 

• • • • 

10.1 

20.0 

Edgewise 

5,992 

t • • • 

• • • • 

10.1 

20.0 

Flatwise 

10,643 

• • • • 

1011 



< < 

17,023 

833 




i i 

8,815 

829 




t i 

8,620 





«< 

11,432 

868 




( ( 

8,907 





a 

6,388 

604 

• • • • 

8.0 

16.1 

< < 

8.144 

• * • • 

642 

9.6 

19.0 

«i 

8,861 

• • • • 

1047 

15.4 

28.1 

Flatwise 

3,779 

308 


14.6 

27.7 

i ( 

5,589 

455 

784 

14.8 

27.9 

Edgewise 

5,192 





Flatwise 

13,511 





<« 

12,907 

• • • • 

• • • • 

11.4 

22.2 

< l 

13,506 

1244 




Flatwise 

7,509 

• • • • 

• » • • 

14.8 

27.4 


6,814 

455 

714 



Flatwise 

20,616 

• • • • 

• • • • 

7.6 

14.6 

(< 

10,950 

• • • • 

• • • • 

9.1 

| 17.6 

i < 

18,574 

• • • • 

• • • • 

6.0 

12.6 

Flatwise 

9,686 





t ( 

12,372 





i i 

11,201 
































































RESULTS OF TESTS ON STONE AND BRICK. 


663 


TESTS OF BUILDING-BRICK AT THE WATERTOWN ARSENAL— continued. 


Description of Brick. 


Eastern Hydraulic Press 
Brick Co.—Philadelphia, 
Pa. 

Shade 200, light buff color. 

Shade 210, slightly darker [ 
thau shade 200 \ '' 

Shade 210 . 

Shade 220, buff. 

Shade 300, buff, darker. 

Shade 300 .. 

Shade 390, gray.. 

Shade 410, light chocolate. 

Shade 410. 

Shade 400 . . . 

Philadelphia and Boston 
Face-brick Co. — Boston, 
Mass. 

Salmon color. 

Light red.. 

Light red. 

Haik i ed..................... 

Chocolate-brown. 

Chocolate brown. 

Cream color.. 

Buff . 

Buff. 

Cray. 


Compression 

Test. 

Cross- 
breaking 
Strength 
in Pounds 
per 

Square 

Inch. 

3 Wl 
f ~ 2 ' bh* 

Shearing 
Strength 
in Pounds 
per 

Square 

Inch. 

Percentage 
of Absorption 

Direction 

of 

Loading. 

Crushing 
Strength 
in Pounds 
per 

Square 

Inch. 

By 

Weight. 

By 

Volume. 

Flatwise 

15,285 

936 

• • • • 

6.9 

14.5 

( < 

13,292 

1232 

1767 



Edgewise 

9,319 





Flatwise 

15,374 

1066 

1097 

5.5 

11.6 

« i 

12,671 

756 

• • • # 

7.9 

16.1 

Edgewise 

9,273 





Flatwise 

13,059 

1038 

988 

7.1 

14.5 

<4 

15,081 





Edgewise 

9,945 

• * • • 

• • • • 

5.5 

11.5 

Flatwise 

12,866 

974 




Flatwise 

3,896 

• • • • 

4 • » « 

19.0 

32.6 

( ( 

8,487 

785 

• • • • 

11.0 

21.6 

Edgewise 

5,877 





Flatwise 

10,942 

1043 

• • • • 

10.0 

20.1 

<4 

7,774 

741 




Edgewise 

17,023 





Flatwise 

3,161 

568 

• • • • 

18.1 

31.0 

4 ( 

8,946 

858 




Edgewise 

4,756 





Flatwise 

3,070 

358 

536 

15.2 

27.1 


In Table XLYI are given the more significant results of a very careful 
series of tests on building brick, these being a part of an elaborate series of 
tests on building materials begun in 1894, and still in progress. These 
brick are supposed to represent the better grades of building brick on the 
market in different parts of this country. The compression tests were made 
by bedding the pressed surfaces in plaster of Paris. A great difference 
will be observed between the crushing strength flatwise and edgewise. 
The strength of these brick, when tested singly, should be compared with 
the strength of brick piers, with various mortars, as shown in Figs. 590 to 
600. 
















































CHAPTER XXXII. 


EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 

439. The Mechanical Tests of the U. S. Timber Investigations.— 

Although timber is the oldest and still the most universally used of all struc¬ 
tural material, no rational determination of the laws controlling the strength 
of timber has been attempted until within a few years. Bauschinger made 
a few experiments in 1882, and pointed the way to a thorough study of tim¬ 
ber which since 1890 has been conducted by the IT. S. Government.* These 
investigations are still incomplete, hut they already furnish a vast amount of 
valuable information, a part of which has been published in bulletins and 
circulars issued by the Forestry Division (Dr. B. E. Fernow, Chief) of the 
U. S. Agricultural Department from time to time. The following direct 
quotations in this chapter are taken from Forestry Circular No. 15, 1897: 

“ The superiority of the data obtained in these investigations lies in (1) 
the correct identification of the material, it being collected by a competent 
botanist in the woods; (2) selection of representative trees with record of 
age, development, place, and soil where grown, etc.; (3) determination of 
moisture conditions, specific gravity, and record of position in the tree of 
the test-pieces; (4) large number of trees and of test-pieces from each tree 
(see Table XLVII); (5) employment of large- and small-sized test material 
from the same trees; (6) uniformity of method for an unusually large num¬ 
ber of tests. 

“ The entire work of the mechanical test series carried on through nearly 
six years intermittently, as funds were available, comprises so far 32 species 
with 300 test trees, furnishing over G000 test-sticks and about 40,000 tests 
in all. f 

“ In addition to the material for mechanical tests, about 20,000 pieces of 
material for physical examination from 780 trees (including the 300 trees 
used in mechanical tests) have been collected to determine structure, char¬ 
acter of growth, specific gravity of green and dry wood, shrinkage, moisture 
conditions, and other properties and behavior. 


* For a short general description of these investigations see Art. 340, p. 402. 
f These tests have all been conducted under the direction of the author in his labora¬ 
tory at St. Louis, Mo. 


604 






EXPERIMENTAL VALVES OF THE STRENGTH OF TIMBER. 665 


TABLE XLYII.—AX ACCOUNT OF THE MATERIAL OPERATED UPON 
(1891-189G) IN THE U. S. TIMBER INVESTIGATIONS. 

(From U. S. Forestry Circular, No. 15.) 


| Number. 

Name of Species. 

Number of Trees. | 

Number of Tests. 

Average 

Specific Gravity 

of Dry Wood.t 

Localities, and Number of Trees from Each. 

1 

Long-leaf pine 

{Pinus palustris) 

* 

68 

6478 

.61 

Alabama—coast plain (22)*, uplands (6), 
hill district (6); Georgia—undulating 
uplands (6); South Carolina — coast 
plain (7); Mississippi—low coast plain 
(2); Louisiana—low coast plain, gravelly 
soil (7). sandy loam (6); Texas—low- 
coast plain (6) 

2 

Cuban pine 

(Pinus heterophylla ) 

12 

2113 

.63 

Alabama—coast plain (6); Georgia—up¬ 
lands (1); South Caroliua—coast (5) 

3 

Short-leaf pine 

( Pinus echinata ) 

22 

1831 

.51 

Alabama — uplands (4); Missouri — low 
hilly uplands (6); Arkansas—low hilly 
uplands (6); Texas—uplands (6) 

4 

Loblolly-pine 

( Pinus tesda) 

32 

3335 

.53 

Alabama—mountainous plateau (8), low 
coast plain (6); Arkansas—level Hood 
plain (5); Georgia—level coast plain (6); 
South Carolina—low coast plain (7) 

5 

White pine 

( Pinus strobus) 

17 

540 

.38 

Wisconsin—clay uplauds (5), sandy soils 
(4), sandy loam (5) ; Michigan—level 
drift-lands (3) 

6 

Red pine (Norway 
pine) 

( Pinus resinosa) 

8 

412 

.50 

Wisconsin—drift (5); Michigan—(3) 

7 

Spruce-pine 

( Pinus glabra) 

4 

696 

.44 

Alabama—low coast plain 

8 

Bald cypress 
( Taxadium distichurn) 

20 

3396 

.46 

South Carolina—pine-barren (6), river-bot¬ 
tom (4); Louisiana—coast plain, border 
of lake (4); Mississippi—Yazoo bottom 
(3), upland (3) 

9 

White cedar 
( Chamcecyparis thyoides) 

4 

354 

.37 

Mississippi—low plain (4) 

10 

Douglas spruce 
(Oregon fir) 
(Pseudotsuga taxifolia) 
( douglasii) 

• • • • 

225 

.51 

Alabama—ridges of Tennessee Valley (5); 
Mississippi—low plain (7) 

11 

White oak 

(Quercus alba) 

12 

1009 

.80 

12 

Overcup-oak 

((Quercus lyraia) 

10 

911 

.74 

Mississippi — low plain (7); Arkansas — 
Mississippi bottoms (3) 

13 

Post-oak 

(Quercus minor) 

8 

256 

.80 

Alabama—Tennessee Valley (5); Arkansas 
—Mississippi bottom (3) 

14 

Cow-oak 

(Quercus michauxii) 

11 

935 

.74 

Alabama—Tennessee Valley (4); Arkansas 
—Mississippi bottoms (3); Mississippi— 
low plain (4) 


* Sixteen of these were bled trees, to study the effects of boxing, 
f The specific gravity here presented is, for ;ill but 8 of the conifers, that of the test- 
pieces onl} r , and is not an average for the material on the whole. 






















666 


THE MATERIALS OF CONSTRUCTION. 


AN ACCOUNT OF THE U. S. TIMBER INVESTIGATIONS— Continued, 


Number. 

Name of Species. 

\ 

Number of Trees. 

Number of Tests. 

Average 

Specific Gravity 

of Dry Wood.* 

15 

Ited oak 

(Quercus rubra) 

5 

299 

.73 

16 

Texan oak 

(Southern red oak) 
{Quercus texana) 

5 

479 

.73 

17 

Yellow oak (black) 

{Quercus velutina) 

5 

222 

.72 

18 

Water-oak ( aquatica ) 
{Quercus nigra) 

4 

132 

.73 

19 

Willow-oak 

(Quercus phellos) 

12 

649 

.72 

20 

Spanish oak 

{Quercus digitata) 

11 

1035 

.73 

21 

Shagbark (sheilbark) 
hickory 

• {Hicoria ovata) 

6 

794 

.81 

22 

Mockernut hickory 
(white) {Hicoria alba) 

4 

300 

.85 

23 

Water-hickory 

{Hicoria, aquatica) 

2 

197 

.,73 

24 

Bitternut hickory 

{Hicoria minima) 

4 

100 

.77 

25 

N utmeg-kickory 

{Hicoria myristicce- 
formis) 

3 

294 

,78 

26 

Pecan {Hicoria pecan) 

2 

172 

.78 

27 

Pignut hickory 

(Hicoria glabra) 

O 

O 

84 

.89 

28 

White elm 

(Ulmus americana) 

2 

91 

.54 

29 

Cedar elm 

(Ulmus crassifolia ) 

3 

201 

.74 

30 

While ash 

(Fraxinus americana) 
Greeu ash ( viridis) 
{Fraxinus lanceolata) 

3 

476 

.62 

31 

1 

45 

62 

32 

Sweet-gum 

(.Liouidambar styra- 
cijlua) 

7 

508 

.59 


Localities, and Number of Trees from Each, 


Alabama—Tennessee Valley (5) 

Arkansas—Mississippi bottom (2); Missis* 
sippi—low plain (3) 

Alabama—Tennessee Valley (5) 

Mississippi—low plain (4) 

Alabama—Tennessee Valley (5); Arkansas 
—Mississippi bottom (3) ; Mississippi— 
low plain (4) 

Alabama—Tennessee Valley (5); Arkansas 
—Mississippi bottom (3); Mississippi— 
low plain (3) 

Mississippi—alluvial plain (3), limestone (3) 


Mississippi—low plain 


Mississippi bottom 
Arkansas bottom 
Mississippi bottom 
Mississippi bottom 

Arkansas—bottom (3); Mississippi— low 
plain (4) 


* The specific gravity here presented is, for all but 8 of the conifers, that of the test- 
pieces only, and is not an average for the material on the whole. 


440. The Investigations still in Progress.—“ As will be observed, some 
species, notably the Southern pines, have been more fully investigated, and 
the results on these (which have been published in more detail in Circular 
No. 12) may be taken as authoritative. With those species of which only a 






























EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 667 


small number of trees have been tested, this can be claimed only within 
limits and in proportion to the number of tests. 

“ The great variation in strength which is noticeable in timber of the 
same species makes it necessary to accept with caution the result of a limited 
number of tests as representing the average for the species, for it may have 
happened that only superior or only inferior material has come to test. 
Hence we would not be entitled to conclude that pignut hickory is 14 per 


cent stronger than shellbark, as it would appear in the tables, for the 30 
test-sticks of the former may easily have been superior material. Only a 
detail examination of the test-pieces or a fuller series of tests would enlighten 
us as to the comparative value of the results. 

“ The following data, therefore, are not to be considered as in any sense 
final values for the species except where the number of trees and tests is very 
large. The variation in strength, as will be seen from the tables, in wood 
of the virgin forest is in some species so great that by proper inspection and 
selection values differing by 25 to 50 per cent may be obtained from different 
parts of the same tree, and values differing 100 to 200 per cent within the 
same species. These differences have all their definite recognizable causes, 
to find and formulate which is the final-aim of these investigations. 


“ The tests are intentionally not made on selected material (except to 
discard absolutely defective pieces), but on material as it comes from the 
trees, so as to arrive at an average statement for the species, when a sufficient 
number of trees has been tested. How urgent is the need for data of inspec¬ 
tion as above indicated will appear from the wide range of results recorded. 

“ To enable any engineer to use the data here given with due caution 
and judgment, not only the ranges of values and the average of all values 
obtained, but also the proportion of tests which came near the average values 
has been stated, as well as the average result of the highest and lowest values 
of 10 per cent of the tests. With this information and a statement of the 
actual number of tests involved, the comparative merit of the stated values 
can be judged. With a large number of tests, to be sure, it is more likely 
that an average value of the species has been found. The actual test results 
have been rounded off to even hundreds in the tables.” 

441. The Moisture Factor in timber w r as described in Articles 192 and 
202. It has been determined by cutting a thin disc from across the entire 
section of the test-stick near the place of failure and finding its weight us 
first taken and after drying at 220° F. In the following tables all values 
have been reduced to a standard moisture of 12 per cent,* which may be 
regarded as that of dry timber out of doors. With all the species tested the 
strength at 12 per cent moisture is some 75 per cent stronger than the same 

* The author is responsible for the reduction of the results on the Southern pines from 
15 per cent to 12 per cent moisture to bring them into harmony with the other test 
results. The former was used as the standard of reference at first, but it was afterwards 
decided this was too high for w’ell-seasoned timber. (See Forestry Circular No. 12 for 
the strength-moisture curves for the Southern pines.) 






668 


THE MATERIALS OF CONSTRUCTION. 


sticks are either green or when wet through after seasoning. In fact, it has 
been shown that water reabsorbed after drying (which is the same as 
seasoning) has the same weakening effect as the original sap. This is 
manifest from Fig. 601, which contains the results of a series of tests on 



Fig. 601.— Showing Variation of Strength of Short-leaf Pine. Sap-wood, with Varying 
Percentages of Moisture both for Drying ami for Reabsorbing Conditions. Tests by 
the author. Drying conditions marked bv a 0 : reabsorbing conditions marked 
by a X. 

identical material tested at various moisture conditions in drying out to a 
nearly zero moisture, and again at similar moisture conditions when moisture 
was uniformly reabsorbed. 

It is the absence of any determination of the moisture condition of the 
test material that vitiates practically all tests of the strength of timber 
except such as have been made by Bauschinger, Tetmajer, and those here 
under consideration. Since large timbers require many years to season, or 
dry, in the open air, while small test sticks dry out very quickly, it is certain 
that the difference in the moisture conditions will fully explain the marked 
differences which have been observed in the strength of identical material in 
different sizes. It is to be hoped that in future all tests of the strength of 
timber will be so made as to fully reveal this condition as a definite percent¬ 
age of moisture across the section near the region of failure. 

In all the tests made by the author, practically identical strength moduli 





















EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 669 


weie obtained on large and small sizes of the same material when they were 
all reduced to the same moisture condition and were equally free from 
defects. Hence tests on small sizes (3 to 4 inches on a side) will give reli¬ 
able factors to use in actual practice. 

As 'shown in dig. 002, the increase of strength with diminishing moisture 


0000 

* 0 

( 

t 

o 










&000 

• 

9i 











«o 

o 

\ ° 









7000 

Sfc '■ 

JO 









1 

o \ 

CP \ 

0 \ 









6000 

% 










1 


o 

V 








6000 



\ 

> 







Si> 


0 


*. 




• 

o 


4000 

X 

§ 



o 

o 



o ° 

35“ 

G 

Nf- 

0 °t 





0 



o 

t . 

0 0 

0 

0 

0 

0 

0000 

/ 



&L- 

OF 

m 

'sm 

?£ 

0 



0 20 40 GO 80 100 


Fig. 602. —Typical Relation between Strength and Moisture of Timber. This diagram 
shows the relation of crushing strength parallel to the grain to the percentage of 
moisture for one species of oak. (From the Author’s U. S. Timber-Test Records.) 

does not become apparent until the moisture percentage becomes less than 
about 40 per cent (and if it were quite evenly distributed it would be at 
about 33 per cent). For a greater percentage of moisture than this the water 
fdls not only the cell-walls (see Art. 194), but also the cell-cavities or lumina. 
Since the weakening effect comes only from the wetting of the walls them¬ 
selves, it follows that after they are fully saturated any excess of water which 
occupies the cell lumina would be inoperative. No increase of strength is 
noticeable, therefore, until the cell-walls themselves (the woody fibre) begin 
to dry out, when the increase of strength becomes very rapid. If this drying 
action could occur uniformly across the entire cross-section of the specimen, 
the locus of the strength-moisture relation would be practically two straight 
lines, one quite straight and parallel to the moisture axis, and the second 
somewhat convex to the strength axis, and intersecting the former locus at 
about 33 per cent moisture. The locus becomes a continuous curve when 
the outer parts dry very much more rapidly than the inner parts, as is the 
case, of necessity, in all processes of drying. To avoid this mixed condition 
it is necessary to make the tests on material absolutely green * or uniformly 

* The “ green ” sticks of the U. S. tests were placed, after sawing in a “wet room,”’ 
where the air was kept at the point of saturation, or as nearly so as possible. 




























670 


THE MATERIALS OF CONSTRUCTION. 


dry (but still containing from 10 to 15 per cent of atmospheric moisture). 
Timber is never uniformly half dry. 


TABLE XLVIII.—STRENGTH OF AMERICAN TIMBER. CONDENSED RESULTS 
OF THE U. S. TIMBER TESTS. ALL VALUES REDUCED TO A STAND¬ 
ARD MOISTURE OF 12 PER CENT OF THE DRY WEIGHT. 

'Compiled from the tables in U. S. Forestry Circular , No. 15.) 





'o' 

& 



Cross-bending Tests. 





Species. 

Number of Trees Tested. 

Number of Sticks Averag 

Specific Gravity. 

Weight per Cubic Foot. 

Apparent Elnstic Limit. 

Ultimate Strength. 

Modulus of Elasticity. 

Crushing Endwise. 

Crushing across Grain 

at Z% Deformation. 

Shearing along the Grain 

1 . 

Long-leaf pine. 

68 

1230 

.61 

38 

lb. sq.in. 
10,000 

lb. sq.in. 
12,600 

lb. sq. in. 

2,070,000 

lb. sq. in. 
8,000 

lb.sq.in. 

1,260 

lb.sq.in. 

835 

2. 

Cuban “ . 

16 

410 

63 

39 

11,100 

13,600 

2,370,000 

8,700 

1,200 

770 

3. 

Short-leaf “ . 

22 

330 

.51 

32 

7,800 

10,100 

1,680,000 

6,500 

1,050 

770 

4. 

Loblolly- “ . 

32 

660 

.53 

33 

9,200 

11,300 

2,050,000 

7,400 

1,150 

800 

5. 

White “ . 

6 

130 

.38 

24 

6 400 

7,900 

11,390,000 

5,400 

700 

400 

6 

Red “ . 

3 

100 

.50 

31 

7,700 

9,100 

1,620,000 

6,700 

1,000 

500 

7. 

Spruce- “ . 

3 

170 

.62 


8,400 

10,000 

1,640,000 

7,300 

.1,200 

800 

8 

Bald cypress. 


655 

.46 

29 

6,600 

7,900 

1,290,000 

6,000 

800 

500 

9. 

White cedar. 


87 

.37 

23 

5,800 

6,300 

910,000 

5,200 

700 

400 

10. 

Douglas spruce.... 


41 

.51 

32 

6,400 

7,900 

1,680,000 

5,700 

800 

500 

11. 

White oak. 

14 

218 

.80 

50 

9,600 

13,100 

2,090,000 

8.500 

2,200 

1,000 

12. 

Overcup-oak. 

10 

216 

.74 

46 

7,500 

11,300 

1,620,000 

7,300 

1,900 

1,000 

13. 

Post- “ . 

5 

49 

.80 

50 

8,400 

12,300 

2,030,000 

7,100 

3.000 

1,100 

14. 

Cow- “ . 

11 

256 

.74 

46 

7,600 

11,500 

1,610,000 

7,400 

1.900 

900 

15. 

Red “ . 

6 

57 

.72 

45 

9,200 

11,400 

1,970,000 

7,200 

2,300 

1,100 

16. 

Texan “ . 

3 

117 

.73 

46 

9,400 

13,100 

1,860,000 

8,100 

2,000 

900 

17. 

Yellow “ . 

5 

40 

72 

45 

8,100 

10,800 

1,740,000 

7,300 

1,800 

1,100 

18. 

Water- “ . 

3 

31 

.73 

46 

8,800 

12,400 

2,000,000 

7.800 

2,000 

1,100 

19. 

Willow- “ .' 

12 

153 

.72 

45 

7,400 

10,400 

1,750,000 

7,200 

1,600 

900 

20. 

Spanish “ . 

5 

251 

.73 

46 

8,600 

12,000 

1,930,000 

7,700 

1,800 

900 

21. 

Shagbark hickory.. 

6 

137 

.81 

51 

11,200 

16,000 

2,390.000 

9,500 

2,700 

1,100 

22. 

Mockernut “ 

4 

75 

.85 

53 

11,700 

15,200 

2,320,000 

10,100 

3.100 

1,100 

23. 

Water- “ 

2 

14 

.73 

46 

9,800 

12,500 

2,080,000 

8,400 

2,400 

1,000 

24. 

Bitternut “ 

4 

25 

.77 

48 

11,100 

15,000 

2,280,000 

9.600 

2,200 

1,000 

25. Nutmeg- “ 

3 

72 

.78 

49 

9,300 

12,500 

1,940,000 

8,800 

2,700 

1,100 

26. 

Pecan “ 

2 

37 

.78 

49 

11,600 

15,300 

2,530,000 

9,100 

2,800 

1,200 

27. 

Pignut 

3 

30 

.89 

56 

12,600 

18,700 

2,730,000 

10,900 

3,200 

1,200 

28. 

White elm. 

2 

18 

.54 

34 

7,300 

10,300 

1,540,000 

6,500 

1,200 

800 

29. 

Cedar- “ . 

3 

44 

.74 

46 

8,000 

13,500 

1,700,000 

8,000 

2,100 

1,300 

30. 

White ash. 

3 

87 

.62 

39 

7,900 

10,800 

1,640,000 

7,200 

1,900 

1,100 

31. 

Green “ . 

1 

10 

.62 

39 

8,900 

11,600 

2,050,000 

8,000 

1,700 

1,000 

32. 

Sweet-gum. 

7 

118 

.59 

37 

7,800 

9,500 

1,700,000 

7,100 

1,400 

800 


















































































EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER . 671 


TABLE XLIX.— CRUSHING STRENGTH OF TIMBER, ENDWISE, IN POUNDS PER 
SQUARE INCH REDUCED TO THE STANDARD PERCENTAGE OF MOISTURE. 

(From U. S. Forestry Circular , No. 15.) 


Species. 

« 

— 

Per cent of Moisture to which Re¬ 
sults are Reduced. 

Number of Tests Averaged. 

Average of all Tests. 

1 

Average of Highest Ten Per cent. 

Average of Lowest Ten Per cent. 

Highest Single Result. 

Lowest Single Result. 

1 Proportion of all Tests within 10 % 
of Average. 

Proportion of all Tests wiihin 25% 

of Average, 

1. 

Long leaf pine. 

15 

1,230 


6,900 

8,600 

5,700 

11,900 

3,400) 

0.53 

0.90 

2. 

Cuban “ . 

15 

410 

* 

7,900 

9,500 

6,500 

10,600 

2,800 ! 

.61 

.93 

3. 

Short-leaf “ . 

15 

330 

1 

5,900 

7,600 

4,800 

8,500 

4,500 l 

.47 

.90 

4. 

Loblolly- “ . 

15 

660 


6,500 

8,700 

5,400 

11,200 

3,900 J 

.49 

.84 

5. 

White “ . 

12 

130 


5,400 

6,800 

4,000 

8,500 

3,200 

.49 

.93 

6. 

lied “ . 

12 

100 


6,700 

8,100 

4,900 

8,200 

4,300 

.54 

.96 

7. 

Spruce- “ . 

12 

170 


7,300 

8,800 

5,600 

10,000 

4,400 

.66 

.95 

8. 

Bald cypress... 

12 

655 


6,000 

8,500 

4,200 

9,900 

2,900 

.31 

.74 

9. 

White cedar. 

12 

87 


5.200 

6,000 

4,400 

6.200 

3,200 

.79 

.99 

10. Douglas spruce. 

12 

41 


5,700 

8,100 

4,200 

8,900 

4. ICO 

.28 

.65 

11. 

White oak. 

12 

218 


8,500 

11,300 

6,300 

12,500 

5,100 

.40 

.81 

12. 

Overcup oak. 

12 

216 


7,300 

8,600 

6,000 

9,100 

3,700 

.70 

.95 

13. 

Post-oak.. 

12 

49 


7,100 

8,100 

6,000 

8,200 

5,900 

.58 

1.00 

14. 

Cow-oak. 

12 

256 


7,400 

9,800 

5,600 

11,500 

4,600 

.51 

.89 

15. 

Red oak. 

12 

57 


7,200 

9,200 

5,500 

9,700 

5,400 

.36 

.94 

16 

Texan oak . 

12 

117 


8,100 

9,800 

6,900 

11,300 

5,800 

.62 

.98 

17. 

Yellow “ . 

12 

40 


7,300 

8,300 

5,800 

8,600 

5,500 

.58 

1.00 

18. 

W:iter- “ . 

12 

31 


7,800 

9.000 

6,300 

9,200 

6,200 

.75 

1.00 

19. 

Willow- “ . 

12 

153 


7,200 

8,700 

5,500 

11.000 

4,200 

.51 

.88 

20. 

Spanish “ . 

12 

251 


7,700 

9,500 

5,100 

10,600 

3,700 

.61 

.94 

21. 

Shagbark hickory ... 

12 

137 


9,500 

10,900 

7,500 

13,700 

5,800 

.79 

.97 

p-> 

Mockernut “ 

12 

75 


10,100 

11,600 

8,000 

12,200 

6,200 

.65 

.99 

23 

Water- 

12 

14 


8,400 

9,600 

7,000 

10,000 

6,700 

.71 

1.00 

24. 

Bitternut “ ... 

12 

25 


9,600 

11,200 

7,800 

11,500 

7,300 

.60 

1.00 

25 

Nutmeg- “ ... 

12 

72 


8,800 

11,000 

7,100- 

12,300 

6,400 

.79 

.97 

26. 

Pecan 

12 

37 


9,100 

10,400 

7,300 

10,000 

5,800 

.51 

.95 

27. 

Pignut ** 

12 

30 


10,900 

12,700 

8,900 

13,000 

8,700 

.72 

1.00 

28 

White elm . 

12 

18 


6,500 

8,800 

5,000 

8,800 

4,900 

.28 

.88 

29. 

Cedar “ . 

12 

44 


8,000 

10,100 

6,500 

10,600 

6,200 

.66 

.95 

30 

White ash. 

12 

87 


7,200 

8,700 

5,700 

9,600 

5,000 

.48 

.96 

31. 

Green “ ... . 

12 

10 


8,000 

9,800 

6,600 

9,800 

6,600 

.29 

1.00 

32. 

Sweet-gum. 

12 

118 


7,100 

8,500 

5,600 

8,900 

4,600 

.60 

.97 


* These results should be increased from 12 to 15 per cent to reduce them to a 


Standard moisture of 12 per cent. See table on p. 670 for results corrected to 12 pei 
cent moisture. 































































672 


THE MATERIALS OF CONSTRUCTION. 


TABLE L.—STRENGTH OF GREEN TIMBER IN COMPRESSION ENDWISE. 

’This timber contained more than forty per cent of moisture. 

(From U. S. Forestry Circular, No. 15.) 


Species. 

Number of 
Sticks Tested. 

Average Com¬ 
pressive 
Strength in 
Pounds per 
Square Inch. 

Highest 
Single Result, 
Pounds per 
Square Inch. 

Lowest 
Single Result, 
Pounds per 
Square Inch. 

1. Long-leaf pine. 

86 

4,300 

7,300 

2,800 

2. Cuban “ . 

38 

4,800 

6,100 

3,500 

3. Short leaf “ . 

8 

3,300 

4,000 

3,000 

4. Loblolly- “ .. 

69 

4,100 

5,500 

2,600 

7. Spruce- “ . 

71 

3,900 

4,700 

2,800 

8. Bald cypress. 

280 

4,200 

8,200 

1,800 

9. White cedar. . 

34 

2,900 

3,400 

2,300 

11. White oak. 

25 

5,300 

7,000 

3,200 

12. Overcup-oak. 

45 

3,800 

4,900 

2,800 

14. Cow-oak .. 

58 

3,800 

4,900 

2,300 

16. Texan oak. 

39 

5,200 

6,000 

3,100 

19. Willow-oak. 

49 

3,800 

5,500 

2.300 

20, Spanish oak. 

52 

3,900 

5,100 

2,500 

21. Shagbark hickory. 

22 

5,700 

6,900 

3,500 

22. Mockernut “ . 

18 

6,100 

7,200 

4,500 

23. Water- “ . 

4 

5,200 

5,600 

4,700 

25. Nutmeg- “ . 

26 

4,500 

5,500 

3,700 

26. Pecan “ . 

4 

3,600 

3,800 

3,300 

27. Pignut “ . 

5 

5,400 

6,200 

4,700 

32. Sweet-gum. 

6 

3,300 

3,600 

3,000 


442. Other Special Investigations.—In addition to regular tests the 
results of which are summarized in Tables XLVIII to LIII, the following 
special investigations have been in progress, the mechanical tests connected 
therewith being under the author’s supervision. Some of the conclusions 
stated below must be accepted as provisional, pending further experiments 
along these lines. 

1. The Effect of “ Bleeding ” (boxing, or tapping, for turpentine) long- 
leaf pine-trees on the qualities of the lumber subsequently cut from the same. 
This investigation included 1300 mechanical tests on bled timber taken from 
two sites, one where the trees had been bled and abandoned for five years, 
and the other freshly bled and abandoned. These results were compared 
with the regular tests on unbled timber. In addition 300 chemical analyses 
were made on bled and unbled timber. These investigations proved beyond 
a doubt that the “ bleeding ” of long-leaf pine timber has absolutely no effect 
on its strength , and probably none on its value or life when exposed to the 
weather. See Forestry Bulletin No. 8. (This conclusion is final. ) 

2. Inflttence of Size on the Strength of Beams. —This investigation included 
433 tests in all. Large beams were first tested to rupture, and then‘small 


































EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 673 

TABLE LI. STRENGTH OF TIMBER IN CROSS-BREAKING. THE MODULUS OF 
RUPTURE REDUCED TO THE STANDARD PERCENTAGES OF MOISTURE. 
POUNDS PER SQUARE INCH. 


(From U. S. Forestry Circular , No. 15.) 


Species. 

Per Cent of Moisture to which the 
Resuhs are Reduced. 

Number of Tests Averaged. 

i 

Average Modulus of Rupture. 

Average of Highest Ten per Cent. 

Average of Lowest Ten Per Cent. 

Highest Single Result. 

Lowest Single Result. 

Proportion of Results within \ 0 % of 

Average. 

Proportion of Results within 25 % of 

Average. 

1. Long-leaf pine. 

15 

1,160 

f 10,900 

14,200 

8,800 

17,800 

3,300] 

0.41 

0.84 

2. Cuban “ . 

15 

390 

J 11,900 

14,600 

8,800 

17,000 

2,900 ' 

.46 

.83 

3. Short-leaf “ __... 

15 

330 

*| 9,200 

12,400 

7,000 

15,300 

5,000 ( 

.40 

.79 

4. Loblolly- “ . 

15 

650 

1.10,100 

13,100 

8,100 

14,800 

3,900 J 

.44 

84 

5. White “ . 

12 

120 

7,900 

10,100 

5,000 

11,100 

4,600 

.43 

.81 

6. Red “ . 

12 

95 

9,100 

12.300 

4,900 

12,900 

3,100 

.28 

.60 

7. Spruce- “ . 

12 

170 

10,000 

13,600 

5,800 

16,300 

3,100 

.43 

.81 

8. Bald cypress. 

12 

655 

7,900 

11,700 

5,000 

14,800 

2,300 

.25 

.69 

9. White cedar. 

12 

87 

6,300 

8,400 

4,000 

9,100 

3,500 

.32 

.78 

10. Douglas spruce. 

12 

41 

7,900 

12,000 

4,100 

13,000 

3,800 

.22 

.58 

11. White oak. 

12 

218 

13,100 

18,500 

7,600 

20,300 

5,700 

.39 

.75 

12. Overcup-oak. 

12 

216 

11,300 

14,900 

6,300 

19,600 

4,900 

.47 

.81 

13. Post- “ . 

12 

49 

12 300 

15,300 

7.400 

16,400 

5,100 

.47 

.92 

14. Cow- “ . 

12 

256 

11,500 

12,500 

6,500 

23,000 

3.300 

.32 

.68 

15. Red “ . 

12 

57 

11,400 

15,400 

9,100 

16,500 

5,700 

.46 

.84 

16. Texan “ . 

12 

117 

13,100 

16,900 

10,000 

19,500 

8,200 

.64 

.86 

17. Yellow “ . 

12 

40 

10,800 

14,600 

5,700 

15,000 

5,100 

.28 

.65 

18. Water- “ . 

12 

31 

12,400 

15,700 

7,200 

16,000 

5,800 

40 

.76 

19. Willow- “ . 

12 

153 

10,400 

13 800 

5,400 

16,000 

3,300 

.33 

.70 

20. Spanish “ . .. 

12 

257 

12,000 

15,600 

6,900 

17,300 

5,000 

.40 

.72 

21. Shagbark hickory. .. . 

12 

187 

16,000 

20,300 

9,400 

23,300 

5,700 

.46 

.84 

22. Mockernut “ .... 

12 

75 

15,200 

19,700 

7,900 

20,700 

5,300 

.45 

.78 

23. Water- “ .... 

12 

14 

12 500 

17,300 

5,400 

18,000 

5,300 

.21 

.64 

24. Bitternut “ .... 

12 

25 

15,000 

19,300 

8,700 

19,500 

7,000 

.28 

.60 

25. Nutmeg- “ .... 

12 

72 

12,500 

15,600 

8,100 

16,600 

6,700 

.40 

.88 

26. Pecan “ .... 

12 

37 

15,300 

18,100 

10,300 

18,300 

5,600 

.38 

.95 

27. Piguut “ .... 

12 

30 

18,700 

24,300 

11,500 

25,000 

11,100 

.43 

.77 

28. White elm. 

12 

18 

10.300 

13,600 

7,300 

14,000 

7,300 

.44 

.72 

29. Cedar- “ . 

12 

44 

13,500 

17,300 

8,500 

19,200 

6,600 

.50 

.86 

30. White ash. 

12 

87 

10,800 

14,200 

6,300 

15,000 

5,000 

.37 

.77 

31. Green “ . 

12 

10 

11,600 

16,000 

5,100 

16,000 

5,100 

.20 

.60 

32. Sweet-gum.. 

12 

118 

9,500 

12,700 

6,000 

14,400 

5,100 

.39 

.79 


* These results should be increased from 12 to 15 percent to reduce them to a standard 
moisture of 12 per cent. See table on p. 670 for results corrected to 12 per cent moisture. 























































































674 


THE MATERIALS OF CONSTRUCTION. 


TABLE LII.— ELASTIC LIMIT STRENGTH OF TIMBER IN CROSS-BENDING AND 

THE MODULUS OF ELASTICITY IN POUNDS PER SQUARE INCH, BOTH 
REDUCED TO STANDARD PERCENTAGES OF MOISTURE. 

(From U. S. Forestry Circular , No. 15.) 


Species. 

Per Cent of Moisture to which 
Results are Reduced. 

Number of Tests Averaged. 

Average Modulus of Elasticity. 

Average Modulus of Elastic 

Strength.! 

Average of Highest Ten Per Cent. 

i 

Average of Lowest Ten Per Cent. 

Highest Single Modulus of Rupture. 

Lowest Single Modulus of Rupture. 

Proportion of Results within 10 % of 

Average. 

Proportion of 'Results within 25 % of 

Average. 

1. 

Long-leaf pine . 

15 

f 1,160 

1.890 000 

8,500 

11 ,00 

5,400 

13,500 

2,400 \ 

0.43 

0.81 

O 

Cuban “ .... 

15 

I 390 

2 , 300,000 

9,500 

r.,5oo 

5,600 

12,900 

2,200 ! 

.42 

.83 

3. 

Short-leaf “ _ 

15 

* ? 330 

1 . 600.000 

7,200 

9,700 

4.800 

11,900 

2,900 f 

.48 

.81 

4. 

Loblolly- “ _ 

15 

L 650 

1 . 950,000 

8,200 

10,800 

5.400 

12,700 

3,100 J 

.46 

.85 

5. 

White “ .... 

12 

130 

1 , J 90.000 

6,400 

8,200 

4.500 

10.000 

4,100 

.58 

.85 

6. 

Red “ . .. 

12 

95 

1 , 620.000 

7.700 

10,300 

4.500 

11.300 

3.100 

.38 

.73 

r* 

4 . 

Spruce- “ _ 

12 

170 

1 , 640.000 

8,400 

11,700 

5,000 

13,700 

3,000 

.51 

.82 

8. 

Bald cypress. 

12 

655 

1,290 000 

6,600 

9,900 

4,200 

12,000 

2,200 

.25 

.66 

9. 

White cedar. 

12 

87 

910.000 

5.800 

7.300 

4.000 

8.200 

3,400 

.44 

.86 

10. 

Douglas spruce.... 

12 

41 

1 , 680,000 

6.400 

9,600 

3,400 

13.700 

2,800 

.32 

.56 

11. 

White oak. 

12 

218 

2 , 090.000 

9,600 

14,100 

6.100 

15.700 

4.400 

.37 

.73 

12. 

Overcup-oak . 

12 

216 

1,620 000 

7.500 

9.500 

5.400 

11,600 

4,000 

.47 

.91 

13. 

Post- “ . 

12 

49 

2 , 030,000 

8,400 

9,600 

6,000 

10,600 

5.100 

.34 

.76 

14. 

Cow- “ . 

12 

256 

1.610 000 

7,600 

11.600 

5,000 

14.200 

3,400 

.50 

.95 

15. 

Red “ . 

12 

57 

1 , 970.000 

9.200 

13,600 

5,600 

14.500 

5,100 

.15 

.49 

16 

Texan “ . 

12 

117 

1 , 860,000 

9,400 

11,400 

7,800 

12,000 

5,950 

.62 

.94 

17 . 

Yellow “ . 

12 

40 

1 , 740,000 

8.100 

11,100 

5,100 

11,800 

4,900 

.35 

.75 

18. 

Water- “ . 

12 

31 

2.000 000 

8,800 

11.400 

5,500 

11,800 

4.500 

.40 

.84 

19. 

Willow- “ . 

12 

153 

1.750 000 

7.400 

10,000 

4,300 

13,100 

2.700 

.42 

.81 

20. 

Spanish “ . 

12 

257 

1 . 930.000 

8,600 

11,600 

6,SOO 

13,500 

5,100 

.41 

.80 

21. 

Shagbark hickory. 

12 

187 

2 . 390.000 

11 200 

14.200 

7,700 

16.100 

5,400 

.50 

.89 

22. 

Mockernut “ 

12 

75 

2 . 320.000 

11.700 

14,600 

7,800 

15,400 

4,300 

.39 

.83 

23. 

Water- 

12 

14 

2 , 080.000 

9 800 

11.800 

4,800 

11.900 

4,100 

..21 

.86 

24. 

Bitternut “ 

12 

25 

2 , 280,000 

11.100 

14,000 

7.600 

14,300 

7.500 

.44 

.84 

25. 

Nutmeg- “ 

12 

72 

1 , 940.000 

9,300 

11,300 

6,400 

12.200 

4 200 

.46 

.93 

26. 

Pecan “ 

12 

37 

2 , 530.000 

11.600 

14.400 

7,900 

15,000 

5,800 

.65 

.89 

27. 

Pignut “ 

12 

30 

2 , 730,000 

12,600 

16.400 

8,300 

17,000 

7,400 

.40 

.83 

28. 

White elm. 

12 

18 

1 . 540,000 

7,300 

9.600 

5,400 

9 700 

5,300 

.33 

.71 

29. 

Cedar- “ . 

12 

44 

1 , 700,000 

8,000 

10,100 

5,800 

10,700 

4,700 

.57 

.91 

30. 

White ash. 

12 

87 

1,640 000 

7.900 

10.400 

5,200 

11.500 

3,600 

.43 

.83 

31. 

Green “ . 

12 

10 

2 , 050.000 

8,900 

13.200 

3.200 

13,200 

3,200 

.40 

.70 

32. 

Sweet-gum. 

12 

118 

1 , 700,000 

7,800 

10,100 

5,100 

11,000 

3,500 

.46 

.82 


* These results should be increased from 12 to 15 per cent to reduce them to a standard moisture 
of 12 per cent. See results corrected to 12 per cent moisture in table on p. 670. 

t This is the Apparent Elastic Limit Strength found as described in Art. 13, p. 18. 


(4-in.) sticks were cut from the uninjured ends, from the top side at one 
end and from the bottom side at the other end. These results prove the 
truth of the proposition announced in (3) on page 462. (This conclusion is 
also probably final.) 





























































EXPERIMENTAL VALUES OF THE STRENOTH OF TIMBER 675 


TABLE LIII.—STRENGTH OF TIMBER IN CRUSHING ACROSS THE GRAIN RE¬ 
DUCED TO STANDARD PERCENTAGES OF MOISTURE, IN SHEARING WITH 
THE GRAIN, IN POUNDS PER SQUARE INCH, THE SPECIFIC GRAVITY, 
AND THE WEIGHT PER CUBIC FOOT, THESE NOT BEING REDUCED TO 
STANDARD MOISTURE. 

(From U. S. Forestry Circular, No. 15.) 


Species. 


1. Long-leaf pine.... 

2. Cuban “ .... 

3. Short leaf “ .... 

4. Loblolly- “ ... . 

5. White “ .... 

6. Red “ .... 

7. Spruce- “ - 

8. Bald cypress. 

9. White cedar....... 

10. Douglas spruce... 

11. White oak. 

12. Overcup- “ . 

13. Post- “ . 

14. Cow- “.. 

15. Red “ . 

1G. Texan “. 

17. Yellow “. 

18. Water- “. 

19. Willow- “ . 

20. Spanish “. 

21. Shagbark hickory 

22. Mockernut “ 

23. Water- “ 

24. Bitternut 

25. Nutmeg- 

26. Pecan 

27. Pignut 

28. White elm. 

29. Cedar- “ . 


30. White ash 

31. Green “ . 

32. Sweet-gum 


Number of 
Tests 
Averaged. 

Crushing- 
strength 
across the 
Grain. 

3 % Deform. 

Shearing- 
strength 
with the 
Grain. 

Average 

Specific 

Gravity. 

Average 

Weight 

per 

Cubic 

Foot. 

1,210 


r 1,000] 

700 

0.61 

38 

400 


l.ooo! 

700 

.63 

39 

330 


900 ( 

700 

.51 

32 

690 


1,000 1 

700 

.53 

33 

130 

700 

400 

.38 

24 

100 

1.000 

500 

.5,0 

31 

175 

1,200 

800 

.62 

39 

650 

800 

500 

.46 

29 

87 

700 

400 

.37 

23 

41 

800 

500 

.51 

32 

218 

2,200 

1,000 

.80 

50 

216 

1,900 

1,000 

.74 

46 

49 

3 000 

1,100 

.80 

50 

256 

1,900 

900 

.74 

46 

57 

2,300 

1,100 

.72 

45 

117 

2,000 

900 

.73 

46 

40 

1,800 

1,100 

.72 

45 

30 

2,000 

1,100 

.73 

46 

153 

1,600 

900 

.72 

45 

255 

1,800 

900 

.73 

46 

135 

2,700 

1.100 

.81 

51 

75 

3,100 

1,100 

.85 

53 

14 

2,400 

1,000 

.73 

46 

25 

2,200 

1,000 

.77 

48 

72 

2,700 

1,100 

.78 

49 

37 

2 800 

1,200 

.78 

49 

30 

3,200 

1,200 

.89 

56 

18 

1,200 

800 

.54 

34 

44 

2,100 

1,300 

.74 

46 

87 

1,900 

1,100 

.62 

39 

10 

1,700 

1,000 

.62 

39 

118 

1,400 

800 

.59 

37 


* These results should be increased from 12 to 15 per cent to reduce them to 12 per 
cent moisture. See results corrected to 12 per cent moisture in table on p. 670. 


3. The Strength of Large Columns as compared ivith the Crushing 
Strength of Short Blochs .—This investigation has not yet progressed far 
enough to enable a definite law to be announced, but they seem to justify the 
column formulae given in Art. 44G, p. 082. 





































































676 


THE MATERIALS OF CONSTRUCTION. 


4. Variation of Strength icith Position across the section of a log, and 
also vertically in the trunk of the tree. These investigations are still incom¬ 
plete. 

5. Relation of Strength to Moisture Condition. —This was made the sub¬ 
ject of a special investigation involving 1806 tests on small sticks two inches 
square. The laws derived from the larger tests were fully borne out. (Con¬ 
clusion final.) 

6. The Uniformity of the Distribution of Moisture in green and dry 
wood. The results showed that in sticks in which the moisture was evenly 
distributed when green it remained evenly distributed longitudinally while 
drying, the moisture percentages having been determined by taking full 
cross-sections J-meh thick entirely across the section. A difference was 
observed in the moisture determinations as between disks £ and f inch 
thick, which the author attributes to the drying effect of the currents of air 
carried by the saw in cutting off the disks, this being relatively greater with 
the thinner sections. For this reason borings are better, but they cannot 
represent equally all parts of the cross-section as does the disk specimen. 
Disks cut with a rapidly moving circular cutting-off saw exhibited the effects 
of this drying action more than those cut with a hand-saw. There is always 
very much more moisture in green sap-wood than in green heart-wood. 

7. The Weakening Effect of Reabsorbed Moisture is the same as that 
originally in the green timber. To determine this 224 tests of strength 
in compression endwise were made on sticks 2 inches square, one half of 
which were on the sap-wood and the remainder on the heart-wood of a single 
slab of short-leaf pine 4 inches thick cut especially for these tests and brought 
at once to the laboratory. Identical material (alternate sections) of sticks 
cut from this plank were used for the diminishing-moisture and for the 
increasing-moisture series, the reduction in moisture being carried to as near 
:zero as was possible for testing in the open air, as the specimens reabsorb 
moisture very rapidly when removed from the dryer. Unfortunately the 
conditions of moisture were not as well distributed as was planned, but the 
results, as plotted in Fig. 601 for the sap-wood, are sufficient to show that 
the weakening effect of a given percentage of moisture is the same whether 
this moisture be the original sap in the tree or whether it be reabsorbed water 
after the timber has been thoroughly seasoned or dried. (Conclusion prob- 
.ably final.) 

It also incidentally developed that the maximum strength corresponds to 
about 3 or 4 per cent of moisture. Since it is impossible to have wood, in 
any kind of service, at so low a moisture percentage (8 or 10 per cent being 
about a normal indoor minimum), this moisture condition of maximum 
strength has no economic significance. 

8. The Effect of Hot-air Drying on Strength. —Two hundred tests were 
made to determine this, with the result that for any temperature commonly 
used in drying lumber no detrimental effect on strength would be produced , 


EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 677 


aside from the checking action which might result from a too-rapid drying of 
the exterior portions of the sticks. (Conclusion probably final.) 

9. The Effect of Very High Temperatures and Pressures used in Drying 
(as in the “ vulcanizing ” process).—In this investigation 210 mechanical 
tests were made on exactly similar material (long-leaf pine 4 inches square), 
a part of which had been submitted to the vulcanizing process in New York 
City, while the corresponding specimens had been dried by an air-blast at 
about 100° F.; many chemical analyses were also made to find if any 
chemical changes had occurred. The results showed a slightly less strength 
for the “ vulcanized ” specimens, for like percentages of moisture, with no 
appreciable chemical change. (Conclusion provisional.) 

10. The Effect of Long Immersion in Water on Strength. —In this inves¬ 
tigation 65 tests of strength have been made on material soaked in water for 
many months and the results compared with those on similar material (alter¬ 
nate sections of the same sticks), which passed through the regular tests. 
So far as these tests go they indicate no loss of strength for six months ’ soak¬ 
ing in water. (Conclusion provisional.) 

Many other special investigations have been planned, but not yet executed 
for want of funds.* 

443. Relations of Weight and Strength.!— “ That within the same 
•species the strength of wood varied with the dry weight (specific gravity), 
i.e., that the heavier stick is the stronger, has been known for some time. 
That this law of variation held good not only for a given species, but from 
species to species, in the pines of our Southern States, was indicated in Cir¬ 
cular No. 12 of this Division. This fact becomes the more important in 
practical application, as the wood of these species of pines cannot as yet be 
disinguished at all by its anatomical structure, and only with difficulty and 
uncertainty by other appearances, while in the lumber market substitution 
is not infrequent. (See Art. 447.) It will, therefore, be best with these 
pines, when strength alone is desired, to inspect the material by finding the 
•specific gravity (or weight per cubic foot), neglecting the species determina¬ 
tion altogether. 

“ While this result of the exhaustive series of tests has been demonstrated 
for these pines and may be considered of great practical value, we can now 
extend the application of the law of relation between weight and strength a 
step farther, and state as an indication of our tests that probably in ivoods 
of uniform structure strength increases with specific weight, independently of 
species and genus distinction; i.e., ceteris paribus, the heavier icood is the 
■stronger. 

* All experimental work stopped in March, 1896. It had been interrupted several 
times previously for lack of means. No special appropriation has ever been made for 
this work. It has all been done with small allotments made from the annual appropria¬ 
tions for the Forestry Division, 
f Dr. Fernow, in Circular 15. 





678 


TEE MATERIALS OF CONSTRUCTION. 


“We are at present inclined to state this important result with caution 
only as a probability or indication until either the test material and tests can 
be more closely scanned, or other more carefully planned and minutely 
executed series of detail tests can be carried on to confirm the truth of what 
the wholesale tests seem to have developed. 

“ In Figs. 603 and 604 the average strength of the different species in 



Fig. 603.— Showing the Relation between Weight and Cnisliing-endwise Strength, of 
Various Timbers at the standard (12%) moisture, except the Southern pines, Nos. 1, 2, 
3, and 4, which are plotted to 15 per cent moisture. ( U. S. Forestry Circular , No. 15.) 

compression endwise and in cross-bending, as found in Tables XLIX and 
LI, has been plotted with reference to the dry weight as given in Table 
XLVIII.* 


“ Considering that these tests and weight determinations (especially the 
latter) were not carried on with that exactness which would be required for 
a scientific demonstration of a natural law, that other influences, as cross¬ 
grain, unknown defects, and moisture conditions, may cloud the results, and 
that in the averaging of results undue consideration may have been given to 
weaker or stronger, heavier or lighter material, the relation is exhibited in 
spite of these wholesale methods with a remarkable degree of uniformity, 
bordering on demonstration. 

“ An exception is apparent in the oaks in that they do not exhibit the 
same relation of strength to weight shown to exist in the other species, and 
also there is a less definite law among the various species of oak when taken 

* The results on the Southern pines, when reduced to 12 per cent moisture, as in the 
table on p. 670, fall from 600 to 1100 pounds higher in Fig. 603 and from 900 to 1700 
pounds higher in Fig. 604.—J. B. J. 



























EXPERIMENTAL VALUES OF TILE STRENGTH OF TIMBER. 679 

by themselves. The structure of oak wood being exceedingly complicated 
and essentially different from that of the wood of all other species under con¬ 
sideration (see Figs. 88 and 123), it may reasonably be expected that this 
species will not range itself with the others. In addition, the difficulty of 



Fig. 604. —Showing the Relation between Weight and Cross-breaking Strength of 
Various Timbers at the Standard (12$) moisture, except the Southern pines, Nos. 1, 
2, 3, and 4, which are plotted to 15 per cent moisture. ( U. S. Forestry Circular , 
No. 15, 1897.) 

seasoning oak without defects, or of even securing perfect material, may have 
influenced the results of tests so as to cloud the ^elationshiu within the genus. 





























680 


TEE MATERIALS OF CONSTRUCTION. 


“ If further close study, supplemented by additional series of tests care- 
fully devised to investigate this relationship, should uphold the truth of it, 
this result may be set down as the most important practical one that could 
he reached by these tests, for it would at once give into the hands of the 
wood-consumer a means of determining the relative value of his material as 
to strength and all allied properties by a simple process of weighing the dry 
material; of course with due regard to the other disturbing factors like: 
cross-grain, defects, coarseness of grain, etc. 

For instance, we would then have, from the results plotted in Figs.. 
603 and 604, approximately: 

Crushing strength endwise of all timbers except the oaks , in pounds per 
square inch — 192 times dry iceiglit hi pounds per cubic foot. . (1) 

Cross-breaking strength of all timbers except the oaks, in pounds per square 
inch — 300 times dry weight in pounds per cubic foot. . . . (2) 

It thus appears that if the above law should be established it will only 
be necessary to determine the weight per cubic foot of any timber (perhaps 
not including the oaks), in order to be able to predict its strength, at least, 
when used for beams and columns 

444. The Factor of Safety to be used in timber-structure designing is. 
now almost wholly a factor of ignorance, a large part of which ignorance it. 
is the object of the U. S. Timber Tests to dispel, as is well stated by Dr. 
Fernow in Circular No. 15, as follows: 

“As to factors of safety it may be proper to state that the final aims of the 
present investigations may be summed up into one proposition, namely, to establish 
rational factors of safety. It will be admitted by all engineers that the factors of 
safety as used at present can hardly be claimed to be more than guesswork. There 
is not an engineer who could give account as to the basis upon which numerically 
the factors of safety for wood have been established as ‘ 8 for steady stress, 10 for 
varying stress, 15 for shocks’ (see Merriman’s Text-book on the Mechanics of Ma¬ 
terials) ; or as 4 to 5 for ‘dead’ load, and 5 to 10 for ‘live’ load (see Rankine’s 
Handbook of Civil Engineering). 

“ The directions for using these indeterminate factors of safety, as given in the 
text-bocks, would imply that the student or engineer is, after all, relying on his. 
judgment as to the modification he should make of such factors ; that is, "he is to add 
to this general guess his own particular guess. The factor of safety is, in the main, 
an expression of ignorance or lack of confidence in the reliability of values of 
strength upon which the designing proceeds, together with an absence of data upon 
which to inspect the material, and a provision for decay. With a larger number of 
well-conducted tests coupled with a knowledge of the quantitative as well as quali¬ 
tative influences of various factors upon strength, and with definite data of inspec¬ 
tion which allow ready sorting of material, the factor of safety, as far as it denotes, 
the residuum of ignorance which may be assumed to remain, as to the character 
and behavior of the material, may be reduced to a minimum, restricting itself 
mainly to the consideration of the indeterminable variations in the actual and legiti¬ 
mate application of load, and to a provision for wear and decay. 

“ While the values given in these tables may claim to contain more elements of 
reliability than most of those published hitherto, much more work will have to be 
done before the above-stated aim will be satisfied.” 


EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 681 


445. Safe Loads for Rectangular Long-leaf Yellow-pine Beams.*—Both 
Prof. Lanza’s tests on wooden beam,-; and those conducted by the author 
show that beams having a shorter length than twenty times the depth under 
a uniformly distributed load, or less than ten times the depth under concen¬ 
trated loads, should be dimensioned for shearing lengthwise. As the total 
load which will cause the beam to shear is independent of the length, when 
shearing occurs before rupture in cross-breaking, the following table gives a 
constant load for all lengths shorter than the least length for rupture in 
cross-breaking. The table is based on a modulus of rupture of 1250 lbs. per 
square inch, or two thirds more than allowed for white-pine beams in 
Carnegie’s Handbook. This is in accordance with the instructions there 
given. It gives a factor of safety of 5 on green beams and of 8 on dry 
beams, when known to be either long-leaf or Cuban yellow (“Georgia”) 
pine. For white pine, cypress, and Oregon fir take 65 per cent of these 

TABLE LIY.—SAFE UNIFORMLY DISTRIBUTED LOADS IN POUNDS ON 


LONG-LEAF YELLOW-PINE BEAMS. BEAM ONE INCH THICK. 

For other thicknesses, multiply the tabular values by the thickness of the beam. 







Depth of Beam 

in Inches. 




Kind 

of 

Stress. 

Span 

Kind 

of 












in 












feet. 

Stress. 

6 

7 

8 

9 

10 

n 

ia 

18 

14 

15 

16 


5 

o 

500 

580 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 


6 

O tD 

500 

580 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 


7 

o a 
a *r 

500 

580 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 


8 

a 2 

-te 0J 

500 

580 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 


9 

co 77^ 

500 

580 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 


Z> 











10 

pH 

500 

580 

670 

750 

830 

920 

1000 

1000 

1080 

1080 

1170 

1170 

1250 

1250 

1330 

53: 

O 

A 

11 


450 

1 580 

670 

750 

830 

920 

1330 


12 


420 

570 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 

O 

13 

r d 

380 

520 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 

E- 

14 

o 

350 

480 

630 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 

fcb 

15 

*3 

330 

450 

600 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 

c2 

16 

H 

320 

425 

550 

710 

\ 830 

920 

1000 

1080 

1170 

1250 

1330 

a> 

17 


300 

400 

520 

670 

820 

920 

1000 

1080 

1170 

1250 

1330 

co 

18 

to 

a 

280 

375 

480 

630 

770 

920 

1000 

1080 

1170 

1250 

1330 

o 

-+-> 

19 

' L5 

270 

350 

470 

600 

730 

880 

1000 

1080 

1170 

1250 

1330 

o 

o 

3 

20 

21 

22 

<n 

& 

250 

330 

450 

570 

690 

850 

1000 

1080 

1170 

1250 

1330 

c o 

•r-• 

c n 

C/3 

o 

O 

240 

320 

425 

540 

650 

810 

950 

11080 

1170 

1250 

1330 

CO 

QJ 

P5 

230 

310 

400 

520 

620 

770 

910 

1070 

81170 

1250 

1330 

23 

o 

220 

300 

380 

490 

600 

730 

870 

1020 

B1170 

1250 

1330 


24 

a 

o 

210 

280 

370 

470 

575 

700 

830 

975 

1140 

1250 

1330 


25 

26 

27 

28 
29 


200 

270 

350 

450 

550 

675 

800 

930 

1100 

1250 

1330 



190 

260 

340 

430 

530 

650 

770 

900 

1060 

1200 

1 1330 



180 

250 

330 

420 

520 

620 

740 

870 

1020 

1150 

1320 



175 

240 

320 

400 

500 

600 

710 

840 

975 

1110 

1270 



175 

230 

300 

380 

480 

580 

680 

820 

930 

1070 

1230 

*-■ * - ***“> 


* See Art. 3466, p. 468a, for weakening effect of permanent loads. 

























































682 


THE MATERIALS OF CONSTRUCTION. 


loads. For short-leaf yellow pine, Norway pine, spruce, oak, elm, and ash, 
take 80 per cent of these loads. 

446. Strength of Wooden Columns.* —A sufficient number of tests of 
columns has not as yet been made by the U. S. Forestry Divisionon which 
to base a general column formula. There was published, however, in the 
Report of Tests made at the Watertown Arsenal for 1882 a very complete 
series of tests of full-size columns, the average results of which are recorded 
iu Tables LVI and LVII and plotted in Fig. G05. There were nearly 200 
columns tested, part being white and part “ yellow ” pine. What particular 
species of yellow pine was used was not determined. Neither was the moist¬ 
ure condition of the timber examined. The sticks had been seasoning 
under cover for about one year. In a number of instances two or three 
sticks were bolted and keyed together, but in no instance did they 

TABLE LV.—SAFE CONCENTRATED LOADS ON LONG-LEAF YELLOW-PINE 


BEAMS. BEAM ONE INCH THICK. 

For other thicknesses, multiply the tabular values by the thickness of the beam. 



Kind 




Depth of Beam in Inches. 





Span 












Kind 

in 

of 












of 

Stress. 

Feet. 

Stress. 

6 

7 

8 

9 

10 

n 

is 

18 

14 

15 

16 
















5 


ImkT 

1580 

670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 

bfi 

6 


430 

570 

| 670 

750 

830 

920 

1000 

1080 

1170 

1250 

1330 

7 


370 

480 

630 

|750 

830 

920 

1000 

1080 

1170 

1250 

1330 


8 


320 

425 

560 

700 

1830 

920 

1000 

1080 

1170 

1250 

1330 

m c 
c ^ 

9 


280 

380 

490 

675 

775 

1920 

1000 

1080 

1170 

1250 

1330 

10 

"d 

a 

o 

250 

340 

440 

560 

690 

840 

11000 

1080 

1170 

1250 

1330 

Q c5 

So 

11 


225 

310 

410 

510 

630 

770 

910 

j 1080 

1170 

1250 

1330 

-*-3 

13 

o 

210 

280 

370 

470 

575 

700 

830 

980 

11170 

1250 

1330 


13 

EH 

190 

260 

340 

430 

530 

650 

775 

900 

1050 

! 1250 

1330 

Cj 

f-H 

14 

fcfj 

175 

240 

315 

400 

490 

600 

720 

840 

970 

1110 

11330 


15 

.2 

a 

165 

225 

300 

375 

470 

560 

670 

780 

910 

1040 

1180 


16 

a; 

160 

210 

275 

355 

430 

525 

625 

730 

850 

980 

1110 

bb 

17 

« 

C/3 

150 

200 

260 

335 

410 

495 

590 

690 

800 

920 

1050 

18 

C/3 

140 

190 

240 

315 

385 

470 

500 

650 

760 

870 

990 


19 

5 

135 

175 

235 

300 

365 

445 

530 

620 

720 

820 

940 

£3 

O) 

20 

O 

125 

165 

225 

285 

345 

425 

500 

590 

680 

780 

890 

oo '‘C 

C/3 S3 

21 

o 

120 

160 

210 

270 

325 

405 

475 

560 

650 

740 

850 


22 


115 

155 

200 

260 

310 

385 

455 

535 

620 

710 

810 

23 

CO 

110 

150 

190 

245 

300 

365 

435 

510 

590 

670 

770 


24 

CD 

HH 

105 

140 

185 

235 

290 

350 

415 

485 

570 

650 

740 

03 r° 

o r- 1 

25 


100 

135 

175 

225 

275 

340 

400 

465 

550 

620 

720 

—j 

’J) 

20 


95 

130 

170 

215 

265 

325 

385 

450 

520 

600 

(»80 

n 

ZJ 

27 


90 

125 

165 

210 

200 

310 

370 

435 

510 

575 

660 

rv* 

28 


90 

120 

160 

200 

250 

300 

355 

420 

485 

555 

635 


29 


90 

115 

150 

190 

240 

290 

340 

410 

465 

535 

615 



* See Art. 3466, p. 468u, for weakening effects of permanent loan*. 















































EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 6^3 

act as one solid stick would have done, but always as two or three single 
sticks would have acted if placed freely in the machine side by side, thus 
proving that in all cases of composite wooden posts they must be treated as 
separate members , each taking its portion of the total load , and deflecting as 
though it stood alone. A great deal of bad and even dangerous designing 
has resulted from violating this principle, and doubtless many fatal accidents 
have resulted from such a practice. It will be observed the composite mem¬ 
bers do not lie appreciably higher in Fig. G05 than the single sticks. Thus 



Fig. 605.—Tests of Full-size Comparatively Green Pine Columns made at the U. S. 

Watertown Arsenal. (See Report for 1882.) Each point plotted represents the 

average of three tests. 

three sticks of yellow pine, 5.5 in. by 11.9 in. and 15 feet long, carried 
• singly an average of 3470 lbs. per square inch. When exactly similar sticks 
were joined in pairs with packing-blocks and bolts, they carried in one test 
3870 lbs. per square inch, and in another test 3530 lbs. per square inch; 
whereas if they had acted as one solid post they should have carried 4300 
lbs. per square inch. When three sticks 4.8 in. by 11.5 in. by 15 feet long 
were packed and bolted side by side, they still deflected sideways, though 
16.4 in. across now in this direction as against 11.5 in. in the other plane, 
and they carried 3110 lbs. per square inch in the one case and 3130 lbs. per 
square inch in the other. If they bad acted as a single stick, they would 
have deflected in the other plane and at a load of 4300 lbs. per square inch. 
Similar results were obtained on white pine as shown in Table LVII and in 
Fig. 605. 

These results also indicate that the author’s parabolic column formula fit 
the experiments as well as any curve could, and hence he has drawn such 
curves in Fig. 605, and there given their equations, these being, for relatively 
green timber: 

Ultimate strength for partially seasoned yellow-pine columns, 


p = 4500 - 1.0 . . 


( 1 ) 
































684 


THE MATERIALS OF CONSTRUCTION. 


Ultimate strength for partially seasoned white-pine columns , 

p - 2500 - 0.5^jj. 

For dry timber these would become: 

Ultimate strength for dry long-leaf pine columns, 

f IV* 

p = 6000 - 1.5UJ. 

Ultimate strength for dry white-pine columns, 

p = 3600 - oW-h ......... (4) 

If somewhat smaller factors of safety be used here than were used in 
the tables of working loads on wooden beams, namely, 6 for dry and 4 for 
green timber, we would have: 

WorJcmg load per square inch for long-leaf pine columns , 

p = 1000 -id)’.< 5) 


. ( 2 > 

• ( 3 ) 


Working load per square inch for white-pine columns , 


p = 60° — ^(^) • 



In all the above equations l — length of column having square ends, and 
h = least lateral dimension of the one or more single sticks of which the 
column is composed, both dimensions taken in the same unit of measure. 

447. How to Distinguish Long-leaf from Short-leaf Pine Lumber. —The 
characteristic indications of these two species of pine become so merged that 
it is impossible to distinguish them when mixed in a consignment. If the 
short-leaf comes up to the long-leaf in specific gravity, in accordance with 
the law laid down in Art. 443, it would not be necessary to distinguish them, 
as they would then be of equal strength and value. As shown by Table 
XLVIII, the average weight per cubic foot of dry long-leaf pine is 38 lbs., 
while that of short-leaf pine is only 32 lbs. But as the lighter specimens of 
long-leaf may be no heavier than the heavier specimens of short-leaf, this is 
not an absolute guide. 

The most nearly absolute criterion is the place of its growth. The long- 
leaf and short-leaf pines do not grow together to any great extent, as shown 
by Plates V and VI. These plates are reproduced from Forestry Bulletin 
No. 13 for the purpose of furnishing this particular criterion. 


* See Fig. 38 '3a, p. 4686, for weakening effect of permanent loads. 












PLATE Y. 

























































































*■ 












































■' 










. 


















i 



> 

a 

o 

- 


X>T A TP TTT 













































































































































































. . 

' 






ill 
















































> 











EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER. 685 


TABLE LYI.—COMPRESSIVE STRENGTH OF UNSEASONED YELLOW-PINE 

COLUMNS. 

(From Rep. Wat. Ars. Tests , 1882.) 


Number of Tests 
Averaged. 

Length of Column 
in Inches. 

Least 

Lateral Dimension 
in Inches. 

Greatest 

Lateral Dimension 
in Inches. 

Ultimate Strength 
in Pounds 
per Square Inch. 

Ratio of Length 
to Radius 
of Gyration. 

Ratio of Length 

to Least Lateral 

Dimension. 

Remarks. 


1 

d 

h 

P 

1 

1 







r 

d 


4 

60 

5.48 

5.51 

4 868 

38 

11 


3 

90 

5.46 

5.58 

4,537 

57 

16 


3 

120 

5.48 

5.50 

4,738 

76 

22 


3 

150 

5.50 

5.51 

5,077 

95 

27 


3 

180 

5.48 

5.50 

3,962 

114 

33 


3 

210 

5.48 

5.48 

3,242 

133 

38 


2 

240 

5.42 

5.46 

2,868 

154 

44 


3 

270 

5.55 

5.57 

2,064 

169 

49 


3 

300 

5.46 

5.58 

1,856 

190 

55 


3 

330 

5.30 

5.31 

1,709 

216 

62 


3 

80 

7.76 

9.78 

4,085 

36 

10 


3 

120 

7.76 

9 74 

4,603 

54 

16 


3 

160 

7.13 

9.74 

3.935 

72 

21 


3 

200 

7.56 

9.65 

4,384 

92 

27 


3 

240 

7.59 

9.68 

3,494 

108 

31 


3 

280 

7.69 

9.75 

3,300 

126 

36 


3 

320 

7.44 

9.28 

2,873 

149 

43 


3 

180 

5.63 

15.6 

3,658 

111 

32 


4 

180 

6.70 

15.6 

3,594 

93 

27 


3 

180 

8.24 

16.2 

3,445 

76 

22 


3 

180 

4.31 

11.5 

2,663 

145 

42 

Sticks like those joined together 

3 

180 

5.52 

11.9 

3,472 

113 

33 

(i << a n << 

3 

180 

5.62 

11.7 

3,869 

111 

32 

2 sticks with 3 packing-blocks 

3 

180 

5.60 

11.7 

3,530 

111 

32 

j 2 sticks with packing-blocks at the £■ 

"J DoilltS 

3 

180 

5.62 

11.6 

3,365 

111 

32 

2 sticks, keyed, with uneven bearings 

3 

180 

4.80 

11.5 

3,110 

130 

37 

3 sticks with 3 packing-blocks 

3 

180 

4.86 

11.5 

3,130 

128 

37 

Same, but swelled f in. at centre 


By demanding the way bills on all consignments coming directly from 
the mills to fill any particular order (which is now the almost universal cus¬ 
tom), one may learn the exact locality of the timber’s growth, and by refer¬ 
ence to Plates V and Y r I a very high degree of probability can be established 
as to the species. As a rule the long-leaf pine is of much slower growth 
than the short-leaf, and hence its annual rings are much narrower. It also 
contains more rosin. Very fair characteristic views of the standing timber 
of these two species may be had from Figs. GOG and 007. The needles of 





























686 


THE MATERIALS OF CONSTRUCTION 



Fig. 606. —Specimens of Long-leaf Pine-trees growing in Open Woods 























EXPERIMENTAL VALUES OF THE STRENGTH OF TIMBER . 


6S? 



Pig. 607.— Specimen of a Sliort-leaf Piue-tree growing in the Open. (Taken from U, 

Forestry Bulletin No. 13.) 












688 


THE MATERIALS OF CONSTRUCTION. 


TABLE LVII.—COMPRESSIVE STRENGTH OF UNSEASONED WHITE-PINE 

COLUMNS. 


(From R<p. Wat. Ars. Tests, 1882.) 




<-« 

_ 


i 




r* 

o 

3 

•s .a 

I 

— 


7} 

12 

H . 

«w ? 

_£ 

G 

a 

0) 

£ 

_ <U 
cSfl 

a 

<Z) 

5 tj 

cS aS 

V" o 

bo ~ 
a ih 

2: a) 
x a 
ca'c 2 

1 ^ 

a 

S m.2 

«M ~ — 

si 

Sf 83 _• 
O 1-5 § 

H as 
«ti eg a 

Remarks. 

o) 5 

53 

r* SJ 

ttfi 

C fl 

1) 

1- o 

D a 

Vj 1. ^ 

4) 1/ C 
-H ^ hH 

cS O 32 

i. 

oat*, 

C> 

o O 1, 

C = 


£ > 
a< . 

“ si _ 

tS j c 
a. 1-1 — 

« CC _ 

.a c a) 
^ .a a« 

a 

c6 O 

% 2 a 


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t-1 

■J 

o 


Ph 




l 

d 

h 

V 

1 

r 

1 

d 

I j 

1 

15 

5.50 

5.50 

3,570 

9.4 

3 

) These sticks were probably dryer than 

2 

GO 

5.48 

5.48 

3,400 

37.9 

11 

) the longer columns 

3 

90 

5.50 

5.50 

2,357 

56.7 

16 

3 

120 

5.46 

5.46 

2,299 

76.1 

22 


3 

150 

5.50 

5.48 

2,643 

94.8 

27 


3 

180 

5.43 

5.43 

2,744 

115 

33 


3 

210 

5.36 

5.36 

1,841 

136 

39 


3 

240 

5.27 

5.28 

1,455 

158 

46 


3 

270 

5.18 

5.19 

1,501 

181 

52 


3 

300 

5.25 

5.25 

952 

198 

57 


3 

330 

5.34 

5.35 

1,080 

214 

62 


o 

O 

80 

7.73 

9.66 

2,527 

35.9 

10 


3 

120 

7.73 

9.70 

2,334 

53 8 

16 


3 

160 

7.66 

9 58 

2,307 

72.4 

21 


3 

200 

7.75 

9.65 

2,225 

89.4 

26 

r 

3 

240 

7.45 

9.40 

2,445 

112 

32 


3 

280 

7.70 

9.62 

2,072 

126 

36 


• > 

° 

320 

7.47 

9.36 

2,113 

148 

43 


3 

180 

5.60 

15.6 

1,874 

111 

32 


3 

180 

6.60 

15.6 

2,204 

95 

27 


3 

180 

8.48 

16.5 

2,222 

74 

21 


3 

180 

4.45 

11.6 

1,672 

139 

40 

Sticks like those joined together 

«( a a it n 

3 

180 

5.55 

11.6 

2,432 

112 

32 

3 

180 

4.50 

11.6 

1,792 

139 

40 

2 sticks with bolts and packing-blocks 

3 

180 

5.60 

11.6 

1,880 

111 

32 

O 4 4 4 4 4 4 (4 44 44 

<0 

3 

180 

5.60 

11.7 

1,991 

111 

32 

2 sticks swelled f in. at centre 

3 

180 

5.60 

11 6 

1,947 

111 

32 

2 sticks and 3 keys, bolted 

3 

180 

5.60 

11.7 

1,974 

111 

32 

2 sticks keyed at the £ points 

3 

180 

5.60 

11.7 

2,102 

111 

32 

j 2 slicks keyed at ends, packed at cen- 
| tre, but with uneven bearings 

3 

180 

4.98 

11.7 

1,746 

125 


3 sticks with 3 packing blocks 

3 

180 

4.86 

11.6 

1,913 

128 

• • 

Same, but swelled f in. at centre 

3 

180 

4.68 

11.7 

1,950 

133 


4 sticks with 3 packing-blocks 

3 

180 

4.88 

11.6 

1,998 

128 

• • 

Same, but swelled f in. at centre 


the long-leaf pine are some 12 inches long, while those of the short-leaf pine 
are only about 2 inches long. 

448. The Strength of Bamboo is very great for its weight, as shown by 
Table LVI1I. Thus, taking 17,300 lbs. per square inch as the apparent 







































EXPERIMENTAL VALUES OF TUE STRENGTH OF TIMBER 6S9 


TABLE LVIII. — STRENGTH OF BAMBOO IN CROSS-BENDING. 

(Tests made by llie author.) 


Outside Diameter between 
Joints in Inches. 

Inside Diameter between 
Joints in Inches. 

Area of Cross-section be¬ 
tween Joints in Square 
Inches. 

Length betweenSupports 
in Inches. 

Number of Joint-lengths 
between Supports. 

Weight of Specimen be¬ 
tween Supports in 

Pounds. 

Modulus of Elasticity in 

Pounds per Square Inch. 

Modulus of Rupture in 

Cross-bending. 

Modulus of Strength at the 

Apparent Elastic Limit. 

Ultimate Deflection of 

Specimen in Inches. 

Deflection at the Apparent 

Elastic Limit in Inches. 

Elastic Resilience in Inch- 

pounds per PoundWeight 

of Specimen. 

1.25 

0.91 


24 

3 

0.539 

2,230,000 

19,600 

13,000 

1.1 

0.54 

156 

1.25 

.98 


28 

3 

.578 

2,200,000 

23,200 

15,800 

3.0 

0.89 

249 

1.16 

.86 


28 

8 

.516 

2,510,000 

25,000 

16,400 

2.0 

0.79 

196 

1.04 

.78 


24 

3 

.375 

2,500,000 

25,800 

15,900 

2.2 

0.65 

182 

0.87 

.63 


22.5 

3 

.266 

2,500.000 

25,800 

17,200 

2.0 

0.73 

205 

0.71 

.51 


25 

3 

.203 

3,020,000 

27,600 

17,200 

2.3 

0.90 

162 

0.40 

.24 


7.5 

1 

.053 

2,100,000 

41,100' 

23,800 

1.1 

0.28 

337 

0.54 

.38 


8.0 

1 

.029 

1,960,000 

30,900 

19,700 

0.65 

0.21 

245 

Menu Values. 

2,380,000 

27,400 

17,300 


216 


elastic limit strength per square inch of bamboo in cross-breakiug (using the 
fl 

formula M — —, and computing /for the actual annular section), we find, 

y i 

by comparing with the results in Table XLVIII, that the strongest timber 
there listed, namely, pignut hickory, is far below it in strength, having a 
modulus at this limit of only 12,600 lbs. If we compare the bamboo weight 
for weight with this, the strongest timber found in the Forestry Division 
tests, to give a certain cross-breaking strength on a given span, as for instance 
28 inches, and taking the timber in the form of a solid rectangular cross- 
section, we find that to carry a load of 440 lbs. at the centre, which was 
carried by the second specimen in Table LVIII, it would require a stick 1.14 
in. square in cross-section. This would weigh 1.4 lbs., whereas the bamboo 
specimen weighed only 0.58 lbs. That is to say, bamboo is just twice as 
strong as the strongest wood in cross-bending, weight for weight , when the 
wood is taken in specimens with a square and solid cross-section. The same 
holds true also for crushing endwise. 

449. The Holding Force of Nails. —One of the most valuable properties 
of wood is the facility with which boards may be attached by means of nails, 
and the strength of such attachments. The holding force of nails and spikes 
in different woods is therefore of considerable importance. In Fig. 608 the 
starting resistances against the drawing out from dry oak wood, of nails hav¬ 
ing different styles of points, are shown graphically. The cut nails exhibit, 
a much greater holding force than do the wire nails, and a slightly sharpened 













































690 


TEE MATERIALS OF CONSTRUCTION. 


point gives the highest resistance for each species. This figure exhibits the 
holding force of different nails, per square inch of embedded surface, when 



Fig. 608.—Relative Adhesive Strength of Wire and Cut Nails (in Oak Wood) as affected 
by the shapes of their points. ( Engr . News, vol. xxxi. p. 24.) 

driven laterally into dry oak wood. Evidently for the softer woods the 
resistance to drawing is very much less, and so is the resistance when driven 
endwise into the stick. 



































































CHAPTER XXXIII. 


STRENGTH OF IRON AND STEEL WIRE, AND WIRE ROPE. 

450. The Strength of Wire increases with repeated drawings, as indicated 
in Fig. 609. As the strength increases the ductility decreases. By anneal- 


WM 

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Fig. 609.— Showing Increase in Strength in Drawing Steel Wire three times from 0.216 

in. to 0.10 in. diameter. (Rep. Wat. Ars., 1890.) 

ing, the ductility is restored and the strength again reduced preparatory to 
further drawing. The final product is given such a temper as its particular 
use demands. 

The increase in the strength of wrought iron with rolling to small rods 
and then drawing through dies is shown in Fig. 610, where the diameters 
vary from 0.8 inch in rolled rods to 0.001 inch in fine wires, the tensile 
strength increasing from 50,000 lbs. to 110,000 lbs. per square inch. 

Fig. 249, p. 309, contains stress-diagrams of steel piano-wires having a 
tensile strength of about 350,000 lbs. per square inch. In the same series 
of tests other wires, about 0.03 inch in diameter, showed a tensile strength 
as high as 447,000 lbs. per square inch.* These wires were of high-carbon 
steel, practically free from sulphur and phosphorus, the chemical composi- 


* Rep. Wat. Ars. Tests, 1894, p. 347 


691 




































692 


TEE MATERIALS OF CONSTRUCTION. 


tion of the strongest wires being: combined carbon, 0.80; manganese, 0.17; 
silica, 0.41; sulphur, 0.015; phosphorus, 0.020. 



The modulus of elasticity of these wires was 28,400,000, showing that 
throughout the entire range of tensile strength of steel from 50,000 to 



Fig. 611.— Average of Nine Tests in Tension on Steel Wires, showing Relation of 

Elastic Limits. ( Wat. Ars. Rep., 1890.) 


450,000 lbs. per square inch the ratio of stress to elastic deformation is prac¬ 
tically constant. 

This material has no “yield-point,” such as is always found with the 
low-carbon steels, as appears from the diagrams in Fig. 611. This diagram 










































STRENGTH OF IRON AND STEEL WIRE, AND WIRE ROPE . 693 

exhibits the advantage of adopting an arbitrary “ apparent elastic limit,” as. 
described in Art. 13, p. 18. As here shown (Fig. 611) this apparent elastic 
limit is well above the true elastic limit, but well below the so-called “ elastic 
limit ” as given in the original published report of this test. It corresponds 
to a permanent set of less than 0.0004 of the length of the specimen, which 
would be quite imperceptible and hence of no significance. The total 
stretch of the specimen at rupture is only 2.8 per cent, or about two per cent 
if measured after rupture. This is the quality of wire commonly employed 
in the manufacture of high-grade wire rope for power transmission, cable 
railways, and the like. Three per cent elongation, measured after rupture, 
is very large for this quality of material. 

Mr. J. Bucknall Smith gives the following average values of the strength 
of iron and steel wires *: 


Lbs. per 8q In. 


Bright hard-drawn iron wire... 80,000 

Bessemer steel wire... 90,000 

Mild open-hearth steel wire . 130,000 

High-carbon open-hearth steel wire. 180,000 

Crucible cast steel wire (patent tempering). 220,000 

Crucible cast steel (plough * quality). 240,000 


“ Bright wire ” is that which remains untreated after the last drawing* 
If it is annealed or tempered in any way after the last drawing, it is left 
black. 

451. The Strength of Steel-wire Rope is difficult to obtain from short 
samples because of the small stretch of the wires, and the fact that some of 
them are more rigidly held than others. In order to grip and hold these ends 
with equal effectiveness various devices have been tried, two of the most 
successful of which are here described. 

The first method is to grip the rope as a whole, without uncoiling the 
ends, by means of grooved wedges moving in a steel-plate holder as shown 
in Fig. 612. This has worked successfully and requires no preparation of 
the specimen. 

The author has used cast-iron and steel holders having conical openings 
for receiving the prepared ends of the cable as shown in Fig. 613. Before 
cutting off the sample it should first be bound tightly with soft wire, some 
six inches from the ends, and then cut off. The intervening length of 
specimen should be wrapped tightly with tarred cord to hold the strands to 
their true position. The ends are then inserted in the sockets, the strands 
opened up, and each individual wire turned back upon itself as shown at the 


* In Mining Journal , June 6—July 11, 1896. 

f So called because it was first used for drawing machine-ploughs in England ; hence 
it is now known as “ plough-steel.” 









694 


THE MATERIALS OF CONSTRUCTION. 


rio-ht of the figure. The ends are then boiled in caustic soda to remove 
all grease, thoroughly washed in hot water, and then dipped in chloride of 


i 

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re 

a 

p 

cr 

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re 

P 

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re 
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3. 8 
4 

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02 O 
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zinc and afterwards in molten solder, thus tinning over each bent wire. 
The ends are then drawn into the conical dies and an alloy of lead, tin, and 
antimony cast around it.* The specimens are now ready to go to the test¬ 
ing machine, where the pulling force is applied to the conical sockets in 
some suitable manner. Split steel sockets, bolted together, may be used if 
preferred. By this means about 95 per cent of the combined strength of 


* Tetmajer uses 8 parts tin, 1 part copper, and 1 part antimony for iron and mild- 
steel wires, while for hard-steel wires of great strength he uses 9 parts lead, 2 parts anti¬ 
mony, and 1 part bismuth. 


























































STRENGTH OF IRON AND STEEL WIRE, AND WIRE ROPE. 695 


the individual wires can be developed in the rope.* If the wedge grips can 
be made to give satisfaction, however, they are much to be preferred. 

In long wire ropes on a straight pull the strength of the rope may be 
taken as about equal to the average strength of the individual wires if these 
are all of about the same ductility and ultimate strength. If the wires differ 
greatly in ductility, the ultimate strength of the rope is the average resistance 
of the wires at that percentage of elongation which corresponds to the total 
elongation of the least ductile samples. It is common to assume the rope to 
have 85 per cent of the total strength of the wires when tested individually. 

Wire-rope pulleys, sheaves, and barrels should have a diameter not less 
than thirty times the circumference (or say one hundred times the diameter) 
of the ropes running upon them, to prevent excessive bending strains in the 
ropes. 

In Table LIX are given a summary of several hundred tests of high-grade 
steel wire and of the ropes it w^as made up into. As these tests were con¬ 
ducted by Prof. Tetmajer with great care, they can be relied on as giving 
the facts for this class of rope. The material found in these specimens, 
which were all taken from ropes actually in service in Switzerland, is superior 
to that usually found serving similar purposes in America. They may be 

TABLE LIX.—RESUME OF TESTS OX CRUCIBLE CAST-STEEL W'IRE AND 
WIRE ROPE USED OX CABLE RAILWAYS IX SWITZERLAXD. 

(From Tetmajer's Communications, vol. iv. p. 272.) 


Test of Entire Cable. (Each Test of Individual Wires, 

the Mean of Two Tests.) (Each the Mean of Eleven Tests.) 




- ® 

G u u 

G 

o 

Tension Test. 

Torsion. 

Bending. 

Ratio of 

Num¬ 
ber of 
Cable. 

Diameter in Inches. 

Tensile Strength i 
Pounds per iSqua 
Inch of Actual Wi 
Section. 

Per Cent of Elongate 
in 8 ft. 

Strength in Pounds 
per Square Inch. 

Per Cent of Elonga¬ 
tion in 20 Inches at 
Rupture. 

Work of Deformation 
in Foot-pounds per 
Cubic Inch. 

Number of Twists (of 
300°) in 8 Inches. 

Number of Bends of 
180° Each on %-in. 
Radius. 

Strength 
of Cable 
to Aver¬ 
age 

Strength 
of Wires. 

1 

1.65 

220,000 

3.12 

265,000 

3.4 

6,400 

27.5 

11.4 

83 

2 

1.67 

117,000 

7.45 

122,000 

9.4 

9,500 

61.5 

11.8 

96 

3 

1.18 

205,000 

2.61 

213,000 

3.0 

4,600 

35.1 

17.8 

96 

4 

1.43 

191,000 

3.30 

207,000 

3.4 

5,000 

44.5 

18.0 

93 

5 

1.00 

184,000 

3.92 

191,000 

3.85 

5.300 

- • . 

15.1 

96 

6 

1.00 

184,000 

3.28 

190,000 

4.0 

5,700 

52.6 

14.8 

97 

7 

1.38 

180.000 

2.37 

222,000 

3.0 

4,600 

33.7 

11.0 

77 

8 

1.30 

226,000 

3.00 

247,000 

3.3 

5,700 

21.7 

9.6 

92 

9 

1.26 

210,000 

3.15 

238,000 

3.3 

5,400 

81.1 

9.4 

89 

10 

1.00 

190,000 

2.40 

190,000 

2.7 

3,400 

48.1 

18.8 

100 

Averages(omit- 
tiug No. 2). 

199.000 

2.98 

217,000 

3.29 

5,100 

36.8 

14.0 

92 


* See article in Engineering, Sept. 11, 1896. 













































696 


TEE MATERIALS OF CONSTRUCTION. 


regarded, therefore, as setting a pattern for American manufacturers to 
strive to attain to.* 

It is the opinion of the author of this work, who has had considerable 
experience in testing high-grade steel wire, that the tension test, taken so a3 

to furnish a complete stress-diagram (as Tet- 
majer took his), furnishes about all the 
information required. The percentage of 
elongation is the best indication of ductility, 
or pliability, and the area of the stress-dia¬ 
gram, reduced to foot-pounds of work done 
per cubic inch of metal as in Table LIX, 
gives the best indication of the value of the 
wire where a very high tensile strength must 
be combined with as great a toughness as 
possible. Xext to this comes the cold-bend¬ 
ing test. The torsion test is, in the opinion 
of the author, of doubtful value, except that 
it may serve to indicate the uniformity of 
the material by testing many samples. The 
most significant result, as indicating wearing 
quality or long life, is the percentage of 
elongation in the tension test. That an 
average strength of individual wires of 
217,000 lbs. per square inch should be 
coupled with an average elongation of 3.29 
per cent would mark an unusually happy combination of strength and 
toughness, were it not for the fact that this elongation was automatically 
recorded, and that it was at rupture and not after rupture. The elastic 
stretch at 217,000 lbs. per square inch would be about 0.8 of one per cent, 
so that if this be subtracted we have only 2.5 per cent elongation if meas¬ 
ured after rupture. This is, however, a high average elongation for such 
great strength. 

Fig. 614 shows an autographic stress-diagram of a high-grade steel wire 
taken by the author on an English wire 0.15 in. diameter, on the machine 
shown in Fig. 615. The diagram gives the following results: 


Ultimate strength in pounds per square inch.= 200,000 

Percentage of elongation in 48 inches.= 2.5 

Work of deformation in inch-pounds per cubic inch.... = 4,000 

Number of twists in 8 in. (torsion test).= 21 

Number of bends of 180° each on -g in. radius (bending 

test).= 3 


* All the instruments used, the methods employed, and the results obtained are given 
in great detail in the original volume. This volume (iv) can now be had only in a 
French translation. 



Fig. 614. 






















STRENGTH OF IRON AND STEEL WIRE, AlSD WIRE ROTE. 69 ? 


By comparison with Table LIX it is seen that this wire is very inferior 
to those there recorded. 

The tension test was made on the machine shown in Fig. 615, while the 
bending test was made on the machine shown in Fig. 617. 



452. Shop Tests of Wire.—The most significant shop tests on wire are: 

1. Tension tests with autographic stress-diagrams. 

2. Cold-bending tests, through 180°, back and forth about jaws having 
a radius of £ inch, or ecpral to the diameter of the wire. 

3. Torsion tests on a length of 8 inches with self-recording attachment, 
giving number of revolutions. 

The instruments shown in Fig. 615 or 616 are very satisfactory for mak¬ 
ing the tension tests. Both give the record complete after the specimen is 
placed and the machine started, without any personal attention whatever. 
In Fig. 615 the poise is operated electrically, while in Fig. 616 the load is 
indicated by the deformation of the heavy spring at the top. This gives also 
the downward dip of the diagram at rupture without any special appliances, 
while in Fig. 616 this is also done by stopping the test and crossing a band 
so as to move the poise backward.* 

The cold-bending machine shown in Fig. 617 is a very satisfactory one. 
By having a number of pairs of jaws with different radii these may always 
be made about equal to the diameter of the wire. A schedule may then be 
prepared for the workman, instructing him to use certain numbers of jaws 
with given numbers of wires. 

The torsion tests are made on a machine like that shown in Fig. 319, 
p. 392. This, however, has no revolution-counter attachment shown 


* Some improvements have now been introduced in this machine by the maker. 






























688 


THE MATERIALS OF CONSTRUCTION. 


Other tests are sometimes resorted to to determine wearing quality. 
Thus Mr. J B. Stone, C.E.,* has arranged a series of small pulleys (about 



Fig. 616.—The Amsler-Laffon & Son Wire-testing Machine, used by Prof. Tetmajer. 

(See his Communications , vol. iv. p. 269.) 

G or 8 inches in diameter), in such relative positions that a wire drawn over 
them is bent alternately in opposite directions. A given tension is then put 
on a loop of wire, and it is run over this series, which is provided with a 


* Of the Washburn Moen Works, at Worcester, Mass. 






























































































































































STRENGTH OF IRON AND STEEL WIRE, AND WIRE ROPE. 699 



revolution-counter, until it breaks. The counter then gives the running 
record of the wire. Mr. Stone then takes the product of the number of 
revolutions into the tensile strength and calls this the “ hoisting value ” of 


Fig. 617.— Wire Setting for Cold-bending Test. 



Fig. 618.— Lang-lay Wire Rope, new. 



Fig. 619.—Lang-lay Wire Rope, well worn. 



Fig. 620.— Ordinary Lay, new. 



Fig. 621.— Ordinary Lay, well worn. 

the wire. For comparing wires of the same diameter he finds by experience 
that this is a good measure of their true worth in service when made into 
ropes, and his experience with this test dates back to 1882, when lie first 

















700 


THE MATERIALS OF CONSTRUCTION. 


TABLE LX.—BREAKING-LOADS AND EQUIVALENT SIZES AND WEIGHTS OF 

WIRE ROPES. 

(From J. Bucknall Smith’s Articles on Wire Rope in Mining Journal, 

Juue 6 to July 11, 1896.) 


Sizes of Ropes, and Approxi¬ 
mate Weigh is per Fathom. 

Calcu¬ 
lated 
Breaking 
Load of 
Ropes. 


c 

C/3 

1) 
a m 
o o 

C c 

HH 

0) P 

P V 

§ o. 

5 ° 
Js« 
o 

Weight of Rope 
made eutirely of 
Wire,per Fathom. 

Weight of Rope 
made with Hemp 
Centre Core, per 
Fathom. 

Best Selected “ Ex¬ 
tra Plough ’’-steel 
Wire. 

Breaking 

Strength 

about 

Compo 

6% 

6)4 

634 

6 

5% 

514 

534 

5 

4% 

4!4 

434 

4 

Pounds, 
UNO Str 

48' 

44 

40 

37 

34 

30 

27 

2514 

24 

22 

1914 

1814 

about 

ANDS 

42 

38 

35 

32 

29 

26 

24 

23 

22 

20 

W14 

16 

Net Tons. 

168 

156 

143 

132 

123 

112 

104 

98 

95 

90 

84 

78 

73 

6% 

6 

5% 

byo 

5% 

5 

4% 

434 

4% 

4 ' 

. . . 

• . . • 

• • • * 

67 

. . • 


.... 

.... 

65 


334 

18^4 

15% 

62 

3% 

m 

17 

1414 

58 

3% 

m 

1514 

1314 

56 


334 

1314 

11% 

54 

314 

a% 

12 

1014 

50 

3% 

314 

10% 

9 

46 

3% 

314 

10 

814 

43 

334 

3 

914 

8 

40 


234 

814 

714 

38 

3 

2% 

8 

rj 

4 

37 


2% 

7 

6%- 

36 


214 

6 

514 

35 

234 

2% 

514 

5 "Vio 

34 


214 

4%o 

4% 

32 

2% 

214 

4 3 /io 

4 

30 


2 

4V 5 

3 8 /xo 

28 

m 

13k 

4 

314 

26 

214 

1% 

3 3 / 6 

3 Vio 

25 


194 


2% 

24 

2 % 

114 


214 

22 


194 


234 

21 

2 % 

134 


1% 

20 


114 


m 

19 

2 

l 


i 

18 


34 


% 

17 


. • 


.... 

16 

i% 




15 

Sheaves and barrels should be 

13 


about 30 

times the 

circumfer- 

12 


ence of the ropes used. 

11 

114 

Notk. — 

For shaft 

winding at 

10 

9^ 

1 % 

a high speed, one tenth of the 

9 


breaking-strength of a rope is 

814 


sometimes taken as fair work- 

8 


ing-load. 

For inclines, the pro- 

r* 

4 

114 

portion of load to breaking 

6 


strength 

varies according to 

514 

114 

gradient conditions, and friction 

5 


should be allowed for. 

414 

... 




334 

- • • 




3 





2 

il*: 

• • 


134 


Circumference of Rope in Inches. 


Best Selected 

“ Plough steel 

Wire. 

Best Selected Im 

proved Patent 

Crucible-steel 

Wire. 

Patent Crucible- 

steel Wire. 

Best Selected Bes 

semer-steel Wire. 

Best Selected Char¬ 

coal-iron Wire. 

6% 

Comp 

ound Str 

• • • 

ANDS 


634 


• . • 

... 

... 

6% 

6% 

. . • 

. . , 

• • • 

6 

614 

• • • 

• • • 

• • • 

5% 

6% 

... 

• • • 

• • • 

514 

6 

• • • 

• • • 

• • • 

5% 

5% 

6% 

• • # 

• • • 

5 

. . • 

6J4 

... 

• • • 

• • . 

514 


• • • 

... 

4% 

514 

6 X 

• • • 

, . . 

. . • 

5 

6 

6% 

... 

414 

... 

5% 

634 

... 

414 

4% 

534 

634 

... 

• • • 

• • • 

5 % 

6 

... 

4 

434 

. « . 

. . . 

6% 


4J4 

5 

5% 

634 

3 34 

• •. 

. . • 

• . . 

... 

4 

4% 

534 

634 

3% 


• • • 

5% 

. • . 

Z% 


414 

5 

6 

334 

3 34 

4% 

4% 

5% 

3% 

3% 

. . . 

. • . 

534 

3% 

3% 

4 

434 

534 

334 

314 

• • . 

4% 

5" 

• • • 

3% 

334 

. . . 

4% 

3~ 

3% 

3% 

4" 

434 

234 

334 

394 

• • • 

• • • 

. • 

3 

314 

334 

434 

2% 

234 

3% 

3% 

4 

2% 


334 

3% 


... 

2% 

334 

334 


214 

2% 

3 


334 

m 

. . . 

. - • 

3 94 

3% 

■ . . 

2 34 

234 

334 

394 

2% 

. . • 


214 

23/4 

2% 

334 

334 

2 

2% 

2 % 

3 

3% 

134 

. . • 

. . • 

2% 

334 

i% 

2 

214 

2% 

3 

134 

2% 

2% 

234 

1% 

1% 

2% 


2% 

• • 

2 

2% 


i}4 

194 

. . • 

.. • 

m 

1% 


134 

2% 

234 

134 

. . • 

234 


, • . 

• . • 

1% 

2 

294 

. • . 


1% 

1% 

234 

m 

• • • 

134 

1% 

2 

Hi 

1% 

1% 

134 

1/4 

• • • 

134 

1% 

194 

. . • 

134 

134 

194 

134 



134 

. • • 

194 

• . . 

• • • 

134 

• • 

• . . 

• • • 

134 

134 


• . 



134 


























































STRENGTH OF IRON AND STEEL WIRE, AND WIRE ROPE. 701 


began using it in St. Louis. This test also indicates the uniformity of the 
wire. If, after rupture, it he hooked up again and then runs a considerable 
time before breaking, it argues a weak spot in the wire which caused the first 
break. If, on the contrary, the first rupture is quickly followed by others 
on further continuance of the test, it indicates that the wire is uniformly 
worn out or fatigued, and that it was very uniform in quality. 

From examinations the author has made on worn-out street-railway 
•cables, he has reached the conclusion that the surfaces of contact with the 
car-grips become highly heated immediately on the rubbing-surface, and the 
resulting local expansion and contraction soon wears out or fatigues the 


metal just under these wearing-surfaces, thus causing the wires to become 
very brittle when bent with these surfaces on the extended side. Certainly 
this extreme brittleness exists at these points, causing the outer wires to 
become all broken up into short pieces, as shown in Fig. 621, before the rope 
finally fails. A shop-test could probably be devised which would determine 
approximately the relative resistance of wires to this kind of action. Running 
ropes of pulleys of too small a radius, thus stressing the outer wires to or 
beyond their elastic limits at every passage, would probably produce similar 
results. 

453. The Albert-lay Rope (commonly called Lang-lay*).—By laying 
up the strands in the same direction as the wires are laid in the strand, the 
rope presents the appearance shown in Fig. 618. Any given outer wire 
remains now on the surface through a much greater distance, and the wires 
wear so as to make a rope almost as smooth as a solid rod, as shown in Fig. 
619. Such a rope is best suited to running on or near the ground, or where 
there is a large amount of grinding surface-wear, as is the case with tail-ropes 
in mines, with inclines, and with tramways. Such a Jay makes a more 
flexible rope also, and larger wires may be used for running over a given size 
of pulley. 


* First used by Prof. Albert, of Claustbal, in 1834. It was patented, however, by 
Lang in 1879 and now commonly bears his name. J. Bucknall Smith in Mining Journal 
articles, June and July, 1896. 



CHAPTER XXXIV. 


THE MAGNETIC TESTING OF IRON AND STEEL. 

By W. A. Layman, M.S. 

MAGNETIC PROPERTIES DEFINED. 

454. Introductory.—Hardly less in industrial importance than the accu¬ 
rate determination of the mechanical properties of iron and steel is the care¬ 
ful testing of their magnetic properties. This arises from the double 
consideration of the vital part played by these properties and the immense 
consumption of iron and steel in what may broadly be termed the electrical 
manufactures. In the construction of electric dynamos, motors, trans¬ 
formers, and other forms of electrical machinery, there have gradually been 
evolved as clearly defined and as rigidly limiting requirements for iron and 
steel along the lines of magnetic permeability and magnetic reluctance or 
hysteresis as are specified by the mechanical engineer in the directions of 
elastic limit, ultimate strength, etc. These requirements are the outcome 
of constant endeavor to lessen the cost of manufacture and increase the 
operating efficiency of electrical apparatus. The use for dynamo-magnets of 
iron or steel possessing high permeability accomplishes the several good ends 
of lessening size, weight, and magnetizing energy required. The use of iron 
in transformer construction with low hysteresis losses means the same econ¬ 
omy in this form of apparatus. Accordingly, iron manufacturers as well as 
electrical engineers are giving much attention not only to the testing of iron 
and steel that the magnetic properties of any given material may be known, 
but also to the study of the physical and chemical conditions which have a 
bearing on these properties, in order that a scientific manufacture of iron 
and steel for electrical work maybe developed. Furthermore, the necessity 
for testing arises from another direction. The design of electrical machinery 
presupposes definite magnetic properties, in every given case, of the iron and 
steel employed. Rut it does not follow that the materials received for use 
can be depended upon to possess these qualities. On the contrary, they may 
vary between wide limits in a given quantity which is commercially of uni¬ 
form quality. A single casting of steel or iron may vary greatly in different 
parts. The same is true of wrought iron, whether rolled in bars or sheets. 

702 


THE MAGNETIC TESTING OF IRON AND STEEL . 


703 


Consequently it is vitally necessary to the successful fulfilment of a designer’s 
predictions that his iron and steel be thoroughly and intelligently tested. 
Otherwise his machine may fall far short not alone in operating efficiency, 
but in ability to carry its rated load. 


455. The Magnetic Properties to be' determined in testing, in the case 
of any given specimen of iron or steel, are the permeability and the hysteresis. 
Permeability is expressed as a ratio, and is the magnetization per unit of 
area, produced, divided by the magnetizing force producing it. For mag¬ 
netizing force the conventional symbol of H is used, and for magnetization 
the symbol B. Both are magnitudes with reference to unit area. In the 
C.G.S. system this unit is the square centimeter, and in the English system 


the square inch. Accordingly, permeability in magnitude is —, and this 

H 


magnitude is symbolized by the Greek letter p. 

Imagine a soft iron bar closely wound from end to end with a magnetiz¬ 
ing coil of insulated wire, the turns of which are uniformly distributed along 
the bar. When an electric current is sent through the coil a condition of 
magnetization is set up in the bar. This condition is numerically expressed 
by the number of magnetic lines of force per unit area of a section of the bar 
near its centre of length, or as B. The magnetizing force is numerically 
expressed by the number of magnetic lines of force per unit of area of the 
enclosed column of air which would take the place of the bar if it were 
removed, or as H. In other words, H is the magnetization produced in air, 
or B for air is equal to H, and p for air is unity. H is determined by cal¬ 
culation from the formula 


OAttCN 


where N is the number of turns in the magnetizing coil, C the current in 
amperes passing through the coil, and L the length of the coil in inches if 
H is expressed per square inch, or in centimeters if H is expressed per square 
centimeter. B is determined experimentally. Permeability is not a constant 
in magnitude, as will be seen from a typical magnetization curve shown in (a) 
of Fig. 622. For example, when H is 4, B is 8000, or p is 2000; but, when 
H is 16, B is only 13,000, or p 812.5. This means that the magnetization 
can be intensified beyond a certain point only at the cost of a rapidly multi¬ 
plying magnetizing energy. 

456. Hysteresis is that property of all forms of iron and steel manifesting 
itself as a reluctance of the magnetization to follow changes in the magnetiz¬ 
ing force. The iron bar above may be used to illustrate. If the bar, in its 
original state, possessed no appreciable magnetization, a constantly increas¬ 
ing magnetizing force would produce a magnetization following the dotted 
curve in Fig. 622 (b). If at the point a the magnetizing force begin to 
decrease, pass through zero, and increase in the negative direction to the 



704 


THE MATERIALS OF CONSTRUCTION. 


value of a positive, the curve instead of returning on itself would follow a 
new path acd in (b) of Fig. 622. If a cyclic operation he performed, the curve 
of magnetization would become a closed loop as in Fig. 622, (c). A study of 
this curve as compared with the same specimen’s magnetization curve would 
reveal a constant dragging of the magnetization behind the magnetizing 
force. This dragging when magnetization is periodic involves an expend¬ 
iture of energy, the enclosed area of the B-H loop as in ( c ) of Fig. 622 multi¬ 


plied by numerically exrwessing this work in ergs per cubic centimeter of 
4 7t 


the metal per cycle. The true cyclic state is not set up at once, but requires 
several repetitions of the cyclic operation, it having been found that the 
original magnetic intensity of a , Fig. 622, (6'), is not at first entirely re- 


(a) ( b ) (a) 



Fig. 622. — Curves illustrating Magnetic Qualities of Iron. {Inst. Civ. Engrs.,. 

vol. cxxvi.) 

stored at the end of the cycle. It is evident now that the area of this 
hysteresis loop depends on the intensity of magnetization produced. In 
other words, for every maximum such as a there will be a definite B-H 
loop. It has been experimentally proved that the locus of a through¬ 
out the range of magnetization is the magnetization curve. This last 
fact will explain the practice hereafter brought out of obtaining the 
magnetization curve by subjecting the iron to reversals of magnetizing 
force and taking half the change of magnetization as equivalent to the 
magnetization which the same force would produce in a previously un¬ 
magnetized piece. Hysteresis losses waste themselves in the production of 
heat within the material. 

All kinds of iron and steel exhibit this property in greater or less degree. 
The softer the specimen of any given material the less in general its hystere- 






































THE MAGNETIC TESTING OF IRON AND STEEL 


705 


sis. For transformer and armature work, accordingly, it is of prime impor¬ 
tance to carefully anneal the plates used. It may here be asked why, in 
work of this class, thin plates are used. The reason is that a cyclic current 
not only sets up a cyclic magnetization in the iron, but also an induced or 
“ eddy ” current in a path parallel to that in which the magnetizing current 
flows. The iron is therefore split up in thin plates in a transverse direction 
to this flow, and the surface oxide of these plates, or a thin coating of japan 
varnish, together with the air-gap thus introduced, are depended on to so 
greatly increase the resistance to flow of these “eddy” currents that they 
become of small importance, practically confining themselves in length of 
path to the thickness of the plate alone. Plates for this class of work are 
rolled in thicknesses varying between .014 and .035 inch. 

The effort has been made to establish a general law by which, the 
hysteresis losses in any given material at any given magnetic induction or 
magnetization being known, the losses at any other induction could be cal¬ 
culated rather than determined experimentally. Exhaustive experimental 
results by Mr. C. P. Steinmetz established the conclusion on his part that, 
within the limits of magnetization employed in general practical work, the 
energy loss by hysteresis increases very closely with the 1.6 power of the 
magnetization. By means of this fact, commonly known as Steinmetz’s 
Law, and the further fact that the hysteresis losses per unit of time 
increase in direct proportion with the increase of rapidity of the cyclic opera¬ 
tion, a reasonably accurate calculation of the hysteresis losses under any set 
of conditions may be made, providing there is an experimental starting-point 
from which to work. 


METHODS OF TESTING. 

457. Measurement of Permeability. —There are in general four classes 
of experimental methods of measuring permeability: 

(1) Magnetometric. 

(2) Balance. 

(3) Inductive. 

(4) Traction. 

Of these (1) and (2) are essentially laboratory methods. In (1) the 
specimen is made up as a bar, surrounded by a magnetizing coil. B is 
determined from observations of the deflections produced by the bar in a. 
magnetometer. In (2) the operation is in general the same with the excep¬ 
tion that a balancing magnet is used to neutralize the effect of the specimen 
under test on the magnetometer. The inductive and traction methods are, 
however, of such character as to permit of more general application. These 
may be considered somewhat in detail. 

458. Inductive Methods. —These are based upon the general principle 
that an electric current will be induced in a given closed path if that path 
or any part of it is made to sweep across a magnetic field. In addition to 


706 


THE MATERIALS OF CONSTRUCTION. 


the magnetizing coil, there is wound upon the specimen of iron or steel a 
small “ exploring” coil. The object sought in all the forms is the sudden 
removal of this exploring coil from the magnetic lines of force embraced by 
it, or, vice versa , the removal of the magnetic lines from the coil. This form 
of test is made upon a specimen ring or long bar of the iron or steel to be 
examined. The variations employed are all attempts to simplify the straight¬ 
forward and accurate form in which the ring is used. 

The Ring Method .—In this method the sample ring is wound with a 
'primary or magnetizing coil and a secondary or exploring coil, each of a 
known number of turns. The general arrangement of apparatus for such a 





Pig. 623.—Arrangement of Apparatus for Permeability Testing by Ring Method. 

(Inst. Civ. Engrs. y vol. cxxvi.) 

test is shown in Fig. 623. Here A is the sample ring under test. It may 
he either of cast iron, wrought iron, or steel as desired, of a single piece in 
thickness or of a number of pieces according to the requirements. Prof. 
J. A. Ewing, ^vho is general authority on this subject, suggests that the 
width of the section of the ring measured radially be small as compared with 
the mean radius. He recommends an external diameter of 3 or 4 inches, 
with a radial thickness of about ^ inch. B is a storage cell for supplying 
magnetizing current; C a two-way switch, in one position of which the cur¬ 
rent flowing will pass into the magnetizing coil of A , and in the other into 
the primary coil of B ; B is an induction-coil, wound on a non-magnetic 
coie, the secondary coil of which corresponds to the secondary or exploring 
coil of A and consists of but a few turns located near the centre of the 












































THE MAGNETIC TESTING OB' IKON AND STEEL. 


707 


primary winding; F is a short-circuiting switch for the D’Arsonval * ballistic 
galvanometer, being employed merely to bring the needle of the galvanom¬ 
eter to rest after an observation has been made; G is a current-meter; K a 
reversing switch by means of which the direction of flow of current in the 
primary winding of A or E may be reversed at will, and also by means of 
which in one position the auxiliary resistance /f 2 may be cut into circuit in 
case the short-circuiting switch S across it is open. 

This arrangement can be used for determining either the magnetization 
curve or the hysteresis loop. The method of procedure in the former case is 
as follows: A definite current, as shown on G, is passed from the battery 
through the primary coil of A, S and A 7 being closed. When a general con¬ 
dition of rest is established for both G and G„ by means of I\ the current is 
several times reversed. On the final reversal F is opened and the swing of 
noted. Half of this swing is taken as representing the magnetization 
produced by the current read. The object sought in the above operation is 
the complete removal of the magnetic lines of force from the specimen. 
Were the current not reversed in direction such would not be the case owing 
to hysteresis, and the galvanometer would only indicate the removal of the 
difference in magnetic lines between that produced by the given current and 
that of the residual charge remaining after the magnetizing force has been 
entirely removed. By reversing the current instead of cutting it off the 
whole magnetic charge is removed and at once reinserted, or. the effect on 
the exploring coil has been equivalent to that of the removal of twice the 


maximum number of lines of force. 

The value of B so determined is translated from the scale of the galvan¬ 
ometer by standardizing the instrument with E. A given current is sent 
through the primary of E and then suddenly cut off. The deflection on the 
galvanometer thereby resulting, due to a current being generated in the 
exploring coil of E, is noted. The magnetizing force H has by this opera¬ 
tion been made to record itself on G 2 . H is at once calculated by the formula 

above given of H = , N being the number of primary turns of E, 


L the length of E , and C the current observed in amperes. From this value 
of H a constant for the galvanometer scale is determined. This constant f 


* This form of galvanometer consists of a coil swinging between the poles of a strong 
horseshoe magnet. The swinging coil carries a mirror, and scale deflections are read 
with a telescope in the usual manner. In damping, the swingiug coil is short-circuited 
by S, and the current then generated in the coil by the swing quickly brings it to rest 
f The deflection produced when any test is made whether on E or A is proportional 
to the product of the induction per unit of area multiplied by the area multiplied by 
the turns of the exploring coil multiplied by a constant. In the case of two tests, one 
on A and one on E , 

d H a'V constant C 
d" — B a"t" constant G 
2 


4 








708 


THE MATERIALS OF CONSTRUCTION. 


K , which is the induction B in the specimen ring for a deflection of one- 

Hal' 

division on the galvanometer scale when a test on A is made, i« K = 

where II is the induction per unit of section of the core of E, a' the area of 
the core of E, t’ the number of turns in the exploring coil of E , a" the sec¬ 
tional area of the specimen ring A, t" the number of turns in the exploring 
coil of A , and d' the divisions deflection on G u when the primary circuit of 
E was broken. 

The calibration of 6r 2 determined, the induction B in a given test on A 
would be the constant K multiplied by the divisions deflection shown on 
the galvanometer scale. H for the magnetizing coil of A with any current 
is calculated from the formula for H as given. The plotting of the entire 
magnetization curve then but requires a series of tests on A alone, the 
current being varied. 

The Divided-bar Method .—This method, due to Dr. Ilopkinson,* is an 
attempt to secure the same results as in the ring method with a much 
cheaper and more easily made specimen. (See Fig. 624. ) Here a heavy block 
of annealed wrought iron Hhas its central portion cut out to receive a mag¬ 
netizing coil C. The test sample of iron or steel SP is made in two parts, 
carefully turned. These parts slide closely through holes bored in the ends 
of the block, and the trued ends meet at the exploring coil E. B is a battery 
for supplying current, A an ampere-meter, S a reversing switch, R an adjust¬ 
able resistance, and BG a ballistic galvanometer. In operation the specimen 
rods are pushed tightly together and magnetized to any point on the sought- 
for magnetization curve. Simultaneously the circuit is now broken and 
the rods pulled apart. The rods separated, a spring at the same instant 
pulls the exploring coil ^entirely out of the magnetic circuit, The effect 
is that of the entire removal of the lines of force from the exploring coil, and 
the whole deflection of BG is accordingly a measure of the induction B when 
BG has been properly calibrated. Dr. Hopkinson’s idea was to make the 
magnetic resistance of the soft iron block so small, as compared with the rods, 
that the condition of the iron circuit would be very nearly the same as if the 
outside ends of the rods were together. His object in making the specimen 
in two pieces was to afford a chance of getting the exploring coil out, other¬ 
wise the magnetic sluggishness of the yoke would have vitiated the re- 


H did" 
2 a"f (V 


or 


B 

<r 


= B per scale division of deflection in test on A — 


H at' 
2a"t"d r 


In this discussion d' and d" are deflections respectively on E and A, and the factors 
TSLat refer to the test on E , while a"t" B refer to A, as above. The factor 2 enters in by 
reason of the deflection d" being made as above explained. 

* Phil. Trans, p 456, 1885. 








THE MAGNETIC TESTING OF IRON AND STEEL. 709 

suits of the tests. The disadvantage involved is the introduction of a very 
thin air-gap where the rods meet and also where they pass through the yoke. 
This introduces an error in the calculation of the true H, for it is evident 
that the magnetizing current must consist of four factors: (1) that required 
to overcome the resistance of the yoke with the given induction B in the 



Fig. 624.—Hopkinson’s Divided-bar Method. (Thompson.) 


rod; (2) that required to overcome the resistance of the air-gap between rods 
and yoke; (3) that required to overcome the break in the rods; and (4) that 
required to overcome the resistance of the rods themselves. (1) may be 
negligible, but (2) and (3) are not. 

The Double-bar Method .—To overcome the objection to Dr. Hopkinson’s 
arrangement, Prof. Ewing has devised a double-bar double-yoke method in 
which the errors involved in the divided-bar method can be experimentally 
determined and allowance then made for them. This is roughly illustrated 
in Fig. 625. The specimen to be tested now consists of two bars, magnetized 
in opposite directions and by equal magnetizing forces, and united by short 
two-part yokes at each end. The two-part yokes, by means of the clamp- 
screws, tightly clamp the specimen bars. The test is made in two parts. 
First the full length of the bars is used, as shown in part (a) of Fig. 625. 
The value of B is determined ballistically, and the magnetizing force 
error included, calculated. The second test is made with the clear length 
of the bars between the yokes reduced to one half, and shorter coils used as 
shown in part (b) of the figure. Now the value of the magnetizing force 
H " is determined for the same value of B as found in the first part of the 
test. The error in the second test is just twice that involved in the first, 
and the correction it is necessary to subtract from IT to give the true mag¬ 
netizing force for the value of B determined in the first trial is H " — //'.* 

* In the first trial HL x — 0.47rC',iV', = H L x -f E. where H is the true magnetizing 


















































710 


THE MA TERfALS OF CONSTRUCTION. 


The Magnetic Bridge Method .—With the object in view of still further 
facilitating and simplifying permeability testing to meet workshop require¬ 
ments, Prof. Ewing has devised another very neat method which he calls the 
“magnetic bridge. ” The principle involved in this method is the production 



Fig. 625. —Ewing’s Double-bar Permeability Method. {Inst. Civ. Engrs., vol. cxxvi.) 

of a magnetic balance, so to speak, between a test specimen and a standard 
specimen, the exact permeability curve of the latter having been previously 
determined by the two-yoke ballistic method above. The process is analogous 
to resistance measurements with the Wheatstone bridge, hence Prof. Ewing’s 
suggested name of the magnetic bridge. The arrangement is illustrated in 
Fig. 626. The two bars, one the test specimen and the other the standard, 
are «, a. Connecting these bars at their ends are heavy yokes of soft iron 
hh\ made in the form of rings and held in place by three longitudinal brass 
rods fff. A cross yoke of soft iron gg, with a central break in it at A, is 
carried up above the end yokes. In the gap h a detector-needle is inserted, 
this being directed by an adjustable magnet k on a brass rod below it. The 


force, C\ the current read, N the turns, L\ the clear length of the specimen bars, and 
E the error introduced by the joint with the yokes and the yoke resistance. 

In the second trial II'L 2 = 0.47r (7 2 iV, = HL 2 -f- E, where Z 2 , (7 2 , and W 2 have 
corresponding values. Since B is the same iu both trials, H is al3o the same. For this 
reason E is the same in both cases. 

From the above 


and 


3 - H+ z: = —cr~' 

tt" _u E 0 AnC?N t 

3 ~ vl + T,= l, ' 


f , • -i tt,, tj, E E 2 E E E 

from which H — H =-- =- - = 

-L-i III hi 1 j\ hi 

Accordingly, H = H' — -=- = H' — {R" - H'). 

h\ 








































































THE MAGNETIC TESTING OF IRON AND STEEL. 


71 I 


bars aa are enclosed by magnetizing coils wound on brass spools. These 
coils are so arranged with switching devices that fractional parts of them 
may be cut in 01 out of circuit at will. The test consists in sending a given 
current into these coils connected in series. If the magnetizations produced 
in the bars are equal, there will be no difference in magnetic 'potential 
between the yokes bb\ But if the magnetizations are unequal, there will be 


h 



Fig. 626.—Ewing’s Magnetic Bridge. (Inst. Civ. Engrs., vol. cxxvi.) 

a difference in magnetic potential between b and b\ and this will manifest 
itself by endeavoring to relieve itself across the soft bar g , thereby producing 
a deflection of the detector-needle. The magnetizing turns over the two 
bars aa are now so adjusted with reference to each other that, on reversal of 
the current, no permanent displacement of the detector-needle is observed. 
The ratio of the two magnetizing forces is then the ratio of the number of 
effective turns employed. B for the standard bar is taken from a table 
accompanying it, the ampere-turns of magnetization being known. The 
permeability for either bar is easily calculated. It is here assumed that the 
measured magnetizing forces are in the same ratio as the real forces, an 
assumption which involves no appreciable error. 

The idea of comparing permeabilities in the two arms of a magnetic cir¬ 
cuit is not new,* but Prof. Ewing is the first to employ this adaptation. The 
only trouble that seems to have been experienced in using this device is a 
“ kick ” on the part of the detector-needle arising from different periods of 
time required for the magnetizations in the standard and specimen bars to 
establish themselves. 

The Voltmeter Method .—This method, as illustrated in Fig. 627, has 
been used by Prof. W. E. Ayrton. The specimen to be tested is made up 
as a bar and slipped into the heavy pole-pieces, a magnetizing coil wound on 
a bobbin sliding over it between the poles. A small armature revolves 


* Trans. Amer. Inst. Elec. Eng., vol. lx. p. 3. 







































































712 


THE MATERIALS OF CONSTRUCTION. 


between the poles at a constant speed, this armature being driven by 8 
small motor. When the specimen is magnetized, the armature generates an 
electric current which flows through the voltmeter. This current is directl) 
proportional to the induction in the bar. From the ammeter-reading the 
magnetizing force H is known, and from the voltmeter-reading the induce 



Fig. 627.— Ayrton’s Voltmeter Method. {Inst. Civ. Engrs., vol. cxxvi.) 


tion B is determined by comparisons made with a standard bar employed 
under exactly the same conditions as to magnetizing force and speed. The 
magnetic curve of this standard bar has been previouslv determined by a 
ballistic method. 

459. Traction Methods. —These methods are based on the fact that when 
magnetic induction crosses, through surface-faces in close contact, from one 

magnetized body to another, these bodies resist being 
pulled apart. The amount of this resistance or “ trac¬ 
tive force ” is dependent on the intensity of the induc¬ 
tion. The traction methods are all directed to the 
simplifying of induction measurements. Of them all, 
perhaps the best known and most generally used is Prof. 
S. P. Thompson’s “ Permeameter ” method. This is 
illustrated in Fig. 628. In general the apparatus closely 
resembles Dr. Ilopkinson’s divided-bar arrangement. 
There is the same heavy yoke and a single magnetizing 
coil. The change is largely in the test-specimen, which 
is now made as a single rod, carefully faced on the 
lower end where it makes close contact against the yoke. 
When a current is sent through the magnetizing coil, 
the rod sticks tightly to the yoke at its lower end. This 
tractive force is measured upon the spring-balance in 
pounds pull required to separate the rod from the yoke. 
B is deduced from the formula B = 1317 VP A- A -f H, 
where A is the area of contact of the rod upon the yoke, 
and P the pull in pounds. H is here added for the 
Fig. 628. — Thomp- reason that the magnetizing coil is not moved with the 
son’s Permeameter. roc ^ as a consequence of which the pull is that due to 
(Thompson.) B — H lines. 

The Magnetic Balance .—This device, due to Dr. II. du Bois, is illus- 









































































































THE MAGNETIC TESTING OF IRON AND STEEL. 


713 


© 3 as will be seen, is divided, the upper portion 

being supported on knife-edges in such a way that an air-gap of definite 
width is introduced between portions of the yoke. The test-bar is inserted 
between the lower detached ends of the yoke. The test is made by moving 
the sliding weights until the rocking part of the yoke is pulled away from 



O' ■ ~ P 

Fig. 629. —Du Bois Magnetic Balance. {Inst. Civ. Engrs., vol. cxxvi.) 

the small stop which determines the air-gap. A curve is furnished by the 
maker of the apparatus for correcting H to compensate for the errors intro¬ 
duced by the air-gap. 

460. Measurement of Hysteresis. —In the measurement of hysteresis 
losses a great variety of methods have been used. In general these have 
aimed at simplicity and facility of testing rather than accuracy. As a result 
they have been more nearly relative than absolute methods. Some have been 
based on the fact that the hysteresis losses waste themselves in the produc¬ 
tion of heat within the iron. In such devices there is always liable to be a 
great inaccuracy arising from the complication of heat being also produced 
by the eddy currents which a cyclic magnetizing current will set up If the 
test-specimen is made of very thin plates, and if the reversals of magnetizing 
currents are not too rapid, this error may be largely eliminated. 

Another series of methods involves the use of an electric wattmeter. 
Here the specimen usually takes the form of a closed magnetic circuit, wound 
with a strong magnetizing coil into which an alternating current is sent. 
By means of the wattmeter the total energy consumed in producing the 
magnetization is observed. Here, again, however, the complication of eddy 
currents enters, as also a loss of energy due to the resistance of the wire. 
This method is nevertheless a very common one in workshops where a sys¬ 
tematic and strictly scientific study of materials has not been entered into. 
By means of an exploring coil to which a voltmeter is attached the induction 
B is known. In the hands of a man who understands thoroughly the use of 
electrical instruments, and who also has a knowledge of the relations existing 
between power, pressure, and current in a circuit carrying an alternating 
current, a wattmeter method will afford no small degree of satisfactory ser¬ 
vice. But in the hands of a less able man it is of little value. 

The Ring Method .—All other methods failing, there remains the straight¬ 
forward ballistic or ring method shown in Fig. 623 and by which perme- 






























































714 


THE MATERIALS OF CONSTRUCTION. 


ability testing was illustrated. For the plotting of the accurate hysteresis 
curve the general method of procedure is but slightly changed. The first 
step is to determine accurately the maximum point a of the loop, Fig. 622 
(6*). This is done exactly as the corresponding point on the magnetization 
curve in Fig. 622 (ft) would be found. After a has been determined, the 
switch A"being on the proper side to permit it, the magnetizing current for 
a is suddenly reduced by any desired amount by simply opening the switch 
S and thereby cutting in A 2 . The magnetization drops in magnitude as 
does the current, but not so far. The full swing of the galvanometer meas¬ 
ures its change. This would determine a single point between a and c, Fig. 
622 (c), dependent on R 2 for its position. Then K is switched over to the 
other side, giving again the full current of a , but reversed in sign and now the 
negative current of d. Next R <2 is changed in value, and then, with S still 
open, K is switched again. The current becomes positive in direction, but 
decreased from the magnitude of d by an amount depending on A 2 . The 
swing of the galvanometer this time determines a point somewhere between 
a and d. Closing S, the magnetization runs back again to ft, and everything 
is in readiness for another cycle. Thus, with each cycle, two points on the 
loop are found, one between a and c, and the other between e and ft. As the 
curve is symmetrical, ac is also de, and ea also dc. Thus the full curve is 
established. 

Ewing"'s Ilgsteresis-tester. —Prof. J. A. Ewing has recently brought 
forward an extremely simple machine for direct measurement of hysteresis 
which he calls a “ hysteresis-tester.” This is illustrated in Fig. 630. The 
sample of iron which is to be tested by comparison with a standard sample 
is prepared by piling about half a dozen 3xf-inch stampings or strips of 
the iron sheet into a bundle, and clamping the same between vulcanite 
washers by the clamps bb on the carrier a. 

This carrier is made to revolve by means of d between the poles of a 
strong permanent magnet e, which magnet is hung on knife-edges in line 
with the axis of the carrier so that it may swing in a concentric arc with the 
carrier a. The magnet is given some stability by a small weight g. Below 
e is a small cup in which a suspended vane swings in oil, thus providing a 
dash-pot. 

The principle involved is that the hysteresis gives rise to a mechanical 
couple between the sample and the magnet, this couple tending to pull the 
magnet around in a circle after the revolving specimen. A deflection from 
a vertical plane results, which deflection is indicated on a scale at the top of 
the supporting post of e. This deflection is a measure of the hysteresis. 
With reference to the operation of the instrument Prof. Ewing says: “ The 
deflection is independent of the speed (so long as that is not so high as to 
cause supplementary deflection by air-currents), and hence no particular 
care has to be taken to turn the handle at a uniform rate. The operator 
has merely to turn the handle just fast enough to make the impulses which 
are given at each half-revolution blend into a steady deflection. The defies 


THE MAGNETIC TESTING OF IRON AND STEEL 


715 


tion is observed first to one side and then to the other hy reversing the 
direction of rotation.” A considerable air-space is left between the ends of 
the sample and the magnet-poles for the purpose of putting practically all 
of the resistance of the magnetic circuit in these gaps, and consequently 
eliminating the permeability of the specimen as a factor. The induction 
used in testing is about four thousand lines per square centimeter. Prof. 



Fig. 630 —Ewing’s Hysteresis Tester. {Inst. Civ. Engrs., vol. cxxvi.) 

Ewing has found that no exact adjustment of the section of the sample is 
necessary, it being sufficient to take that number of strips which come nearest 
in weight to the standard sample which is furnished with the instrument. 

A small error is involved, probably due to the fact that there is some; 
hysteresis in the magnet itself when the sample is revolving.” 

The objection to the instrument is that tests can only be made at a single 
induction. To this objection Prof. Ewing has replied that Steinmetz’s Law, 
within the range of inductions usually obtaining, affords easy translation to 
any induction desired. All in all the instrument is certainly a valuable 
addition to the magnetic testing apparatus now at command. 
















716 


TEE MATERIALS OF CONSTRUCTION. 


RESULTS OF TESTS 

461. Development Due to Testing.—Magnetic tests have established 
relationships between the various forms of iron and steel manufactured, which 
are depicted in the typical curves of magnetization and hysteresis presented 
in Figs. 631 to 635 inclusive. These curves are worthy of close study, as 
from them may be read not only the characteristic magnetic differences 
between the various forms of steel and iron, but also the story of many radi¬ 
cal changes that have quickly succeeded each other in the manufacture of 
electrical machinery. Fig. 631 alone, for example, will explain why the 



generating dynamo of to-day, with only from one half to three quarters the 
volume of magnetic material in it, is equal in electrical capacity to the 
dynamos of ten years ago. This fact is evident from the magnetic superi¬ 
ority of cast steel over cast iron. In the early manufacture of dynamos and 
motors, the field-magnets and connecting yokes were made entirely of cast 
iron. The magnetic superiority of wrought iron was soon more generally 
appreciated, and pole-pieces were then forged, where manufacturing facili¬ 
ties permitted. This was a distinct gain, but as a considerable part of the 
magnetic circuit was still of cast iron because all parts of the dynamo 
frame, for mechanical reasons, could not be forged, much was still to be 
desired from the standpoint of magnetic economy. Forged steel, having no 






























THE MAGNETIC TESTING OF IRON AND STEEL. 


717 


magnetic advantage over wrought iron, afforded no improvement. Cast 
steel, however, developing practically as high permeability as either wrought 
iron or forged steel, except with very weak magnetizing forces, at once 
accomplished the great advantage sought. The entire framework, pole- 
pieces and yokes included, could be easily cast, and the result has been the 
adoption, where facilities permit, of cast steel for all forms of electrical 
machinery calling for solid rather than laminated parts. Within the last 
two years a still further improved form of dynamo-magnet construction has 
been introduced, mention of which only can be made here. This is the 
building up of the magnetic polar projections of the field-frame of laminated 
wrought iron or steel. These poles are then placed in their proper relative 
positions in the mould for the field-frame, and the cast steel for the remain¬ 
ing parts poured around them. The object sought is the elimination of the 
eddy currents, which are induced in the pole-faces when the machine is in 
operation. 

Fig. 632 will especially make clear why there is such a marked superiority 



Fig. 632._Curves showing Relative Hysteresis Quality of Three Specimens. (Inst. Civ. 

Engrs., vol. cxxvi.) 

of one alternating-current transformer over another of the same general 
dimensions, a fact generally known but not generally understood. In this 
figure are given the hysteresis curves of three different makes of iron 
furnished for the same class of work. The tests were made by Prof. Ewing. 
I was furnished as soft wrought iron, but the curve discredits this claim. 
It will be seen that III is vastly superior to II, while I as compared 
with either III or II is exceedingly poor. Fig. 635 still further em- 















718 


THE MATERIALS OF CONSTRUCTION. 


phasizes how marked may be the differences between materials, under a 
cyclic magnetization, all supposed to be commercially suitable for the same 
class of work. Here are given both magnetization and hysteresis curves, the 
results being taken from a recent paper by Prof. Ewing.* I is a special 
grade of Swedish transformer iron, from which Prof. Ewing makes the 
standard bars used with bis liysteresis-tester; II is a transformer-plate of 
steel; III, another quality of Swedish transformer iron; IV, a transformer- 
plate made from scrap-iron; and V, a specimen of iron wire used by Mr. 
Swinburne some years ago in the manufacture of bis “hedgehog” trans¬ 
former. From these curves is further evident the cause of much of the 
great improvement that has been made in the efficiency of all forms of 
apparatus where hysteresis is involved. 

462. Conditions Affecting Magnetic duality.—Careful testing has fur¬ 
nished much information as to the conditions which affect the magnetic 
^quality of iron and steel. Of these conditions, which may in general be 
classed as physical, great magnetic differences in materials are sometimes 
due. For example, permeability is seriously affected by such operations as 
'hammering, rolling, etc. A given specimen of soft annealed iron may have 
its permeability greatly reduced by the hardening resulting from stretching. 
In the same way, steel, hard drawn, has much lower permeability than steel 
annealed. With cast metal the suddenness of cooling, in similar manner, 
seriously affects the magnetic quality. Material under excessive strain also 
has its permeability lowered. As a general rule, the warmer the metal the 
lower its permeability. That the hysteresis-factor is also seriously affected 
by many of these same conditions is more generally appreciated. Hence 
the electrical manufacturer’s effort to carefully anneal his iron. 

The part played by chemical composition is not so well understood. The 
fact of the matter is that as yet the study of magnetic quality from the 
standpoint of chemical composition has not been systematically or exhaus¬ 
tively entered into. But few results of value in this direction are at com¬ 
mand. Accordingly, a recent paper by Mr. H. F. Parshall f is of unusual 
value, as it contains results of a great many tests in which chemical composi¬ 
tion was very closely considered. Mr. Parshall calls attention to the fact, as 
brought out in his results, that, “ beginning with the most impure cast iron 
and passing tlnough the several grades of cast iron, steel, and wrought iron, 
the magnetic properties accord principally with the amounts of carbon 
present, and in a lesser degree with the properties of sulphur, phosphorus, 
manganese, and other less usual ingredients; and that an excess of any one 
or of the sum of all the ingredients (other than iron) has a noticeable effect 
on the magnetic properties.” Fig. 634 is here produced from Mr. Parshall’s 
results to support his conclusions, as also to indicate the general magnetic 
qualities of the materials tested. In this direction it may be stated as a 


* Proc. Inst. Civil Engrs., vol. cxxvi. p. 184. 
t Proc. Inst. Civil Eng., vol. cxxvi. p. 220. 


4 




THE MAGNETIC TESTING OF IRON AND STEEL . 


719 


generally observed fact that the purer the iron the higher the permeability. 
Results of tests by Prof. Ewing in curves II, III, and IV of Fig. 633, 



Pig. 633.—Magnetization Curves showing Relation between Wrought Iron and Steel. 



Fig. 634.—Parshall’s Results showiug Effect of Impurities on Magnetization. 


although the chemical compositions are not given, may be said to bear out 
this fact. 

With reference to hysteresis loss m laminated iron, there has recently 
been shown to exist in many qualities of material a gradual deterioration 
under the conditions imposed by continued service. Of such a striking 









































720 


TEE MATERIALS OF CONSTRUCTION. 


nature is this change that much attention is being paid to it. Cases are on 
record in which the hysteresis losses in transformers under heavy service have 
increased over 100 per cent. Mr. Parshall cites one case in which, during 
two years’ service, the increase was about 200 per cent. Many observations 
bearing on this property of iron and steel are given by Mr. Parshall. His 
tests covered six months’ service, in general, of the samples of material under 
examination. The magnetic induction was closely the same in all speci¬ 
mens, while the temperature of service varied. Several specimens gave no 
evidence of change whatsoever. Others changed as much as 25 per cent. 
Chemical analysis only indicated a difference in the percentage of silicon 
present, but whether the change is related to or dependent on the silicon 
cannot now be positively stated. Taking this change of quality into 
account, it may be seen that the manufacturer of transformers has two con¬ 



siderations involved in the selection of his iron or steel plate. First, the 
quality of material with reference to permeability and hysteresis, and second 
the quality of material with reference to permanency of magnetic properties 
under continued service. It is possible for the change in quality to take 
from materials greatly superior, on first examination, all of the superiority 
possessed by them. More data are badly needed upon this phase of the 
subject. 

463. In Conclusion the reader is again invited to closely study all the 














































THE MAGNETIC TESTING OF IRON AND STEEL. 


721 


curves presented. They are plotted from accurate and authentic tests, and 
show not alone the relative qualities and absolute magnetic values of the 
various forms of steel and iron, but also many elements which the special 
needs of the investigator may lead him to search for. Furthermore, the 
data are almost entirely new, which gives a still greater value. 

It is also desired to place great emphasis on the need as well as desir¬ 
ability of thorough, accurate, and continued magnetic testing of materials. 


TABLE LXI.— USEFUL DATA OX ELECTRICAL CONDUCTIVITY, ETC. 



Electrical Conductivity. 

Specific Gravity. 

Specific Heat. Average 

at Ordinary Tempera¬ 

ture. (Regnault.) 

Fusion Pts. in Degrees 

Fahr. 

Coefficient of Thermal 
Conductivity. (Wie- 
| demann ahd Franz.) 

At Normal Tem¬ 
peratures. 

(Lezare Weiler.) 

Mathi 

u 

A 

a 

o O* 

O CO 

-4-J 43 

< <J 

essen. 

u 

rC 

. c$ 

o o 
o 

O t-h 

7—( 

<5 <1 

Pure silver. 

100 

100 

71.56 

10.505 

0.0570 

1733 to 1873 

100 

Pure copper. 

100 



8.853 

0.0951 

1929 to 1996 

73.6 

Refined and crystallized copper. 

99.9 

99.95 

70.27 





Telegraphic silicious bronze. 

98.0 







Alloy of copper and silver (50#). 

80.65 







Pure gold. 

78.0 

77.96 

55.90 

19.258 

0.0324 

1913 to 2285 

53.2 

Silicide of copper, 4* Si. 

75.0 







Silicide of copper, 12# Si . 

54.7 





i 

37.96 

Pure aluminum . 

54 2 



2.67 

0.2185 

1157 \ 

to 

Tin with 12* of sodium. 

46.9 





l 

38.87 

Telephonic silicious bronze.... 

35 0 







Copper with 10* of lead. 

30.0 







Pure zinc. . 

29.9 

29.02 

20.67 

7.00 

0.0956 

680 to 779 


Telephonic phosphor bronze... 

29.0 







Silicious brass, 25* zinc. 

26.49 







Brass, 35* zinc . 

21.5 







Phosphor-tin . 

17.7 







Alloy of gold and silver (50*) . .. 

16.12 







Swedish iron. 

16.0 







Pure Banca tin. 

15.45 

12.36 

8.67 

7.35 

0.0562 

442 to 446 

14.5 

Antimonial copper. 

12.7 







Aluminum bronze (10*). 

12.6 







Siemens steel . 

12.0 







Pm-p nl n.t i n 11 m. 

10 6 

18.00 


21.5 

0.0324 

3227 

8.4 

Copper with 10* of nickel . 

10.6 







Cadmium amalgam (15*) . 

10.2 







Dronier mercurial bronze . 

10.14 







Arsenical copper (10*) . 

9.1 







Pure lead . 

8.88 

8.32 

5.86 

11.38 

0.0314 

608 to 618 

8.5 

Bronze with 20* of tin . 

8.4 







Purp mVkpl . 

7 89 



8.8 

0.10863 



Phosphor-bronze, 10* tin . 

6.50 






19.2* 

Phosphor-copper, 9* phosphor... 

4.90 





i 

Antimony . 

3.88 

4.62 

3.26 

2.67 

0.0508 

• 

810 to 1150 < 

to 

21.5 

'Wprrmrv ... 


1.60 


13.58 

0.0333 


67.7* 










* Calvert & Johnson. 




























































722 


THE MA TERIALS OF CONSTRUCTION. 


On the scientist’s part this necessity is fully appreciated, for he understands 
that just as the present knowledge of their magnetic properties and the suc¬ 
cessful use of iron and steel in the electrical manufactures is the result of 
careful testing, so also is future development along these lines dependent on 
testing. On the manufacturer’s part there is a constantly growing appre¬ 
ciation of the great advantages to be gained from testing. The electrical 
manufacturer, knowing how great may be the variation in magnetic quality 
of the materials furnished him, is keenly alive to the fact that he cannot 
maintain nor advance the standard of his apparatus without testing. The 
iron and steel manufacturer, in turn, is coming to see that he cannot much 
longer furnish for electrical work such materials as are included in his regular 
line of manufacture. Electrical work is beginning to demand rather than 
accept, and soon must have materials which are shown by scientific study to 
best meet the requirements of this department of industry. The situation 
is one in which the consumer must not only protect himself, but lend all the 
assistance within his power to the scientific study of magnetic phenomena, 
while the iron manufacturer must, by the limitations of trade competition, 
know from his own investigations the quality of the materials he is turning 
out and the part played by physical and chemical conditions of manufac¬ 
ture. From every point of view is clearly evident the importance of the. 
magnetic testing of iron and steel. 


APPENDIX A. 


A BIOGRAPHICAL SKETCH OF THE LIFE OF PROFESSOR JOHANN 

BAUSCHINGER.* 

Professor Bauschinger was born in Niirnburg in 1834. His father was an 
artisan, and bad a large family. Young Bauschinger, therefore, at an early age 
saw the earnest side of life, and he learned to have faith in his ability to support 
himself. At the age of fourteen he began giving private lessons. However, gifted 
with a strong will-power, he completed the course at the Polytechnic School with 
honors in 1853 at the same time receiving his certificate from the Latin School. 
Having selected mathematics and physics as the branches which he desired eventually 
to teach, he studied for three years at the University of Munich. Under von Lamont 
he studied with great enthusiasm theoretical and practical astronomy. He had the 
rare opportunity of using the astronomical and magnetic instruments in the royal 
observatory at Bogenhausen. Here he developed that faculty of keen observation 
and learned the scientific methods of discussing and reducing observations to obtain 
the most probable results, which afterward stood him in such good stead. 

In the fall of 1856, after having passed the examinations for teacher in matne- 
matics and physics, he accepted the position as assistant in physics and descriptive 
geometry at the Polytechnic School in Augsburg, and in 1857 he was called to 
Fiirth, where he became teacher of mathematics and physics at the Royal Industrial 
School. 

In 1866 Bauschinger was transferred to the Academy in Munich, and two years 
later he became professor there of mechanical engineering at the newly-founded 
Technical School. In 1870 he became director of the testing laboratory, which was 
built under his direction and according to his plans. Here he remained and labored 
in the interest of. science until his death. 

At Fiirth Bauschinger had already developed a literary activity. Papers by him 
on subjects pertaining to mechanical engineering and thermodynamics appeared in 
various publications. As an independent work he published his popularly-written 
School of Mechanics. This was followed in 1871 by The Elements of Graphical 
Statics. 

Without doubt Bauschinger’s best and most valuable publications were those 
relative to his physical tests. His Indicator Trials on Locomotives had been begun 
as early as 1865, and they were continued at Munich under extreme difficulties on 
account of the great amount of work he was called on to perform as professor m 
the Technical School. However, Bauschinger’s main field of investigation was in 
the testing of materials. Here he earned great and indisputable fame. 

His writings since 1871, published in the Journal of the Society of Bavarian 
Architects and Engineers and other publications, and later in his Communications 
from the Testing Laboratory of the School of Technology of Munich, will long fur¬ 
nish ample data for the study of the strength of materials. His was the first public 
testing laboratory in all Germany, and it has continued to stand as the most noted 
in the world in many respects. This institution, with its furnishings, has served as 
a model for all later similar establishments 


* Compiled by the author from a more extended memoir by Prof. A. Martens, and published in the 
Digest of Physical Tests for July, 1896. 


723 





724 


APPENDIX. 


Bauschinger greatly improved our means for testing materials by the invention 
'of accurate measuring apparatus, one example of which was his application of the 
Gauss method of mirror readings, by which all measurements are very accurately 
obtained. Many other accurate measuring and testing devices, now commonly 
'employed, are due to him. 

Referring now to his contributions to the science of the strength of materials, in 
his “ Communications” we may say, in short, that in the numbers 1, 4, 5, 7, 8, 10, 
11, 18, and 19 he treats of the strength of cements, mortars, and artificial and nat¬ 
ural building-stones. In numbers 1, 7, and 8 Bauschinger speaks of his numerous 
tests of cements, and cement and lime mortars. In these, as well as in the tests 
of artificial and natural stones discussed in numbers 4, 5, 10, and 11, 18, and 19, 
different methods were used, and the various results were compared. He has made 
a special study of the elasticity and strength of building-stones. At the same time 
and in the most detailed manner he made cross-bending, tension, compression, and 
shearing tests of the same materials. 

For the investigation of the wearing of stones an abrasion method was devised 
(see Art. 430, p. 645). The effects of freezing are minutely examined and compared, 
and many simplifications are given to the conscientious worker. 

In No. 6 of the “Communications” are treated the laws of compression. Besides 
discussing the older works of the French and English, his own experiments are given. 
In other numbers, 2, 3, 13, 20, and 21, the properties of metals, the law of the 
resisting power of iron and stone columns in fire (numbers 12 and 15), and the 
methods of testing to determine the mechanical properties of wood (numbers 9 and 
16), etc., are discussed. The change of the elastic limit and strength of iron and steel 
due to stretching and crushing is especially to be noticed (number 13). 

The “ Conventions for the Agreement as to the Methods of Testing Building and 
Construction Material,” of which lie was president, were entirely due to his ener¬ 
getic action. The reports of these meetings are contained in numbers 14 and 22 of 
Ms “ Communications,” the latter of which he did not live to complete. These 
conventions led directly to the permanent International Association which has since 
been organized. 

Ilis work was recognized in all parts of the world. He was made member of the 
Royal Prussian Academy of Architects, also of the Royal Bavarian Academy of 
Science in Munich and of the Imperial Academy of Naturalists at Halle ; also honor¬ 
ary member of the American Society of Mechanical Engineers, of the Royal Im¬ 
perial Technological Industrial Museum in Vienna, and of the Royal Bavarian 
Industrial Museum in Nurnburg, etc., etc. 

He died on the 25th of November, 1893, after having given the scientific world 
the results of his experiments, his theories, and his improveihents in testing- 
machinery, which will ever stand as an indestructible monument to his memory. 


APPENDIX B. 


STUDY OF IRON AND STEEL BY MICROGRAPHIC ANALYSIS. 

By Prof. J. O. Arnold, Sheffield, Eng. 

I. Popular* 

The ever-increasing severity of engineers’ specifications, framed to secure trust¬ 
worthy qualities in metals used for structural purposes, has undoubtedly had the 
effect of stimulating metallurgists to make closer scientific investigations, having 
for their object the determination of the fundamental laws governing the chemical 
physics of metallic alloys, and the exact working of those laws with reference to"the 
ultimate mechanical properties of metals. More particularly in connection with 
iron and steel, the fact is now generally recognized that materials identical in 
chemical composition may possess widely different mechanical properties. When 
the observations of the analytical chemist, although indispensable, nevertheless 
became of more limited value, the metallurgical physicist appeared on the scene 
and, it must be confessed, very ably put forward a theory that the otherwise inex¬ 
plicable differences in the practical properties of chemically identical masses of iron 
or steel must be due to allotropic changes in the iron itself, and, for a time, allo- 
tropic molecules became fashionable. When, however, practical metallurgists found 
that the allotropic school put forward as part of their belief the startling creed that 
chromium and tungsten, silicon, sulphur, and phosphorus soften steel, it became 
evident that, as far as the practical applications were concerned, there was a rift in 
the theoretical lute, and that the indication, furnished by some other line of re¬ 
search were destined to explain the puzzling effects frequently observed. 

During the last few years it has become more and more apparent that the veil 
would only be lifted from the mysteries of metals by micrographic analysis—a fact 
of peculiar interest and encouragement to young experimenters starting along the 
thorny path of research. Young scientists, after executing and publishing patient 
Rnd valuable work, will often find that their efforts are received with indifference. 
Such investigators should remember that the micrographic analysis of iron and 
.steel was inaugurated thirty-five years ago by Dr. Sorby, in a research which, for 
patience of execution and sterling value of results achieved, has seldom been ex¬ 
celled. The sagacity of Dr. Sorby’s preconceived idea, that metals should be re¬ 
garded as crystallized igneous rocks, is now generally recognized. Nevertheless 
practical metallurgists have only quite recently realized that Sorby’s research 
founded the science of metallography. This science is destined in the near future 
to become an indispensable adjunct to chemical analysis, and it has already practi¬ 
cally proved that the metallurgical engineer, instead of groping for the causes of 
abnormal mechanical effects in the outer darkness of molecular metaphysics, may 
often readily find such causes well within the range of actual vision by means of a 
cheap microscope. 

In a word, the venue of trial has been changed from molecules to crystals, or, to 
be more strictly accurate, from molecular to intercrystalline cohesion, or, it may be, 
.adhesion. The magnitude of this change is hardly capable of mental realization, 
but its enormity may be vaguely grasped by recalling Lord Kelvin’s calculation of 


* From Iron and Coal Trades Review, 1896. 







7 26 


APPENDIX. 


the probable approximate dimensions of a molecule, namely, that if a single drop 
of water be magnified up to the size of the earth, the constituent molecules of the 
drop would be somewhere about the size of marbles. It is encouraging to know 


that the growing importance of micrographic analysis has become a matter of 
international recognition, and among patient investigators engaged in its develop¬ 
ment in America, England, France, Germany, and Holland may be mentioned the 
names, respectively, of Stead, Osmond, Martens, and Behrens. There is little doubt 
that the efforts of these and other workers will soon raise metallography to the rank 
of a definite science, but the path of the student seems likely to be rendered neces¬ 
sarily difficult by the assignation of names to apocryphal constituents, and the 
curse of synonyms already hovers over the science. 

Many people are inclined to associate the microscopic examination of steel with 
a grave peering into fractures with a hand lens. It is well to clearly understand 
once and for all that the fracture of a piece of steel or iron has but little correla¬ 
tion with its ultimate structure. The latter is ascertained, firstly, by obtaining a 
perfectly polished section of the metal; secondly, by delicately etching with acid 
the prepared surface, in order to reveal the constituents, just as the structure of a 
macadamized road is revealed after a heavy flush of rain. The results so far ob¬ 
tained by this method of examination have proved that even a chemically pure 
metal is not, a homogeneous solid, being built up of a number of primary metallic 
crystals, which may themselves break up into a large number of secondary crystals. 
It is extremely probable that the mechanical properties of such a metal are measured, 
not by molecular cohesion—not even by the cohesion between the secondary crys¬ 
tals—but by the attractive force acting between the facets and the large primary 
crystals. 

Passing on to the question of the so-called alloys, the indications of the micro¬ 
scope have already gone far to negative the generally accepted idea that an alloy 
consists of a homogeneous solution of one metal in another, or of a non-metallic 
element in a metal. To take the specific case of steel in its ordinary state, as 
used for structural purposes, the microscope has forever removed from the mind 
of the engineer any idea that he has to deal with a homogeneous mass. To bring 
steel into its purest and essential form, in which iron and carbon are the main 
constituents, the microscope has proved that steel is grown from iron by gradually 
increasing the carbon present, and that it reaches maturity, otherwise a compara¬ 
tively homogeneous mass of true steel, when the percentage of carbon approximates 
0.9 per cent. This percentage constitutes the critical microscopical point of steel, 
and has been named the “ saturation-point.” The addition of more carbon pro¬ 
duces a supersaturated steel, slowly progressing towards pig iron. However, 
structural engineers are more immediately concerned with unsaturated steels—that 
is to say, steel containing less than 0 9 per cent of carbon. In such material, what 
may be called a semi-critical point of great importance, from an engineer’s view, is 
presented in iron containing 0.45 per cent of carbon. The material then consists of 
an intimate mixture of perfectly distinct crystals of iron, and of true steel contain¬ 
ing 0.9 percent of carbon, in equal proportions. This metal presents mechanical 
properties intermediate between those of pure iron and true steel. Should an engi¬ 
neer in his specification demand a carbon higher than 0.45 per cent, he will obtain a 
material possessing the characteristics of steel rather than those of iron. On the 
other hand, in metals containing less than 0.45 per cent of carbon the character¬ 
istics of iron will predominate. The above statements have reference to an ideal 
case, the consideration of which is, however, absolutely necessary to form the base¬ 
line of steel metallurgy. In practice the case becomes complicated because of the 
presence in structural steels of from 0.5 per cent to 1 per cent of manganese. The 
influence of the quantity Inst named on the mechanical properties of steel is well 
known, and its effect on the microscopic structure is remarkable. Nevertheless, it 
seems to have escaped the observation of most steel microscopists. There is little 
doubt that the observed effects are due to the formation of a remarkable triple 
compound of iron, manganese and carbon. 

Our knowledge of this subject is far from complete ; it is, in fact, a branch of 
the subject requiring immediate and rigorous investigation. It is, however, certain 
that in iron containing 1 per cent of manganese the microscopic saturation-point 


STUDY OF IKON AND STEEL BY MICROGRAPHIC ANALYSIS. 727 


marking the conversion of the iron into a homogeneous compound, steel, appears, 
about 0.65 per cent of carbon. We have in this fact a satisfactory explanation 
of the well-known mechanical differences between Swedish and English Bessemer 
spring-steel of like carbon, the kinder properties of the Swedish material being due 
to the fact that it contains only about ^ per cent of manganese. Further investiga¬ 
tions, not yet ripe for publication, have gone far to indicate that the specific action 
of the elements nickel, chromium, tungsten, and silicon are due, not to the ele¬ 
ments per se , but to a remarkable series of double carbides of the respective elements 
with iron. The substances above mentioned are, however, often useful when em¬ 
ployed to obtain the mechanical properties demanded by unusually severe specifi¬ 
cations. But the steel metallurgist is confronted by the invariable presence of two 
elements, the action of which is always injurious, frequently to an extent seemingly 
out of all proportion to the percentages present. Speaking broadly, sulphur is the 
more deadly enemy, for reasons which open up a wide field of research in general 
metallurgy. The cause of the more injurious action of sulphur may be stated in a 
word. Sulphide of iron, which (and not sulphur) is the substance with which the 
engineer has to reckon, is far more fusible than phosphide of iron. The extent to 
which mass fragility may be produced by very small quantities of a fluid or semi-fluid 
constituent, after the main mass of the material has solidified, is hardly capable of 
exaggeration, and microscopical evidence will presently be published which will 
conclusively prove that proportions of sulphur hitherto deemed harmless may, under 
certain conditions, produce a remarkable mass weakness fully capable of account¬ 
ing for mysterious and disastrous effects. Sulphide of iron is incapable of adherence 
to the constituents adjacent to it within the mass, so that the extent of its injurious 
effects will depend upon the form in which it exists mechanically. Its least in- 
jui^ous form is that of fused globules, which are practically equivalent to minute 
blowholes. Its most dangerous form is that of attenuated membranes enveloping 
groups of crystals, and forming long lines of weakness equivalent to minute cracks. 
The mechanical distribution of the semi-fluid sulphide during the rolling and ham¬ 
mering of steel presents dangerous possibilities and requires rigorous microscopical 
investigation. 

A fruitful field of research which has already yielded important results is the 
microscopical determination of the changes taking place during annealing. The 
constituents chiefly involved in this change are the carbides and sulphides, and the 
results already obtained have completely negatived the accuracy of the generally 
accepted theory of annealing. It is not intended in the present article to antici¬ 
pate, by premature publication, the remarkable influence of annealing on the distri¬ 
bution of sulphide of iron, and the increase in mechanical strength following such 
redistribution. With reference to carbides, however, it may be pointed out that in 
one of our leading text-books on metallurgy the toughening influence of the process 
of annealing is attributed to three causes : 1. A change of hardening carbon into car¬ 
bide carbon. 2. A breaking up of large crystals into minute crystals. 3. A distribu¬ 
tion of carbide carbon from crystalline pellets into finely-diffused particles. Micro¬ 
graphic analysis has shown that not only are the foregoing statements inaccurate, 
but they are also opposed to fact, for the following reasons : 1. There is no harden- 
'n<>- carbon in steel castings. 2. The crystals become much larger on annealing. 
3.°The carbide carbon is entirely concentrated into crystalline pellets. The above 
case is a single example of the light destined to be thrown on the metallurgy of 
steel by micrographic analysis. It, however, yet remains for engineers to fully 
grasp the realities briefly set forth in this article. To do so it is necessary to 
examine a comprehensive collection of properly prepared iron and steel micro- 
sections.* The recognition of the value of the science to metallurgical engineers has. 
undoubtedly been retarded by a pedantic adherence to the reproduction of the struc¬ 
tures observed by photography. 

It seems that the idea that the camera is the George Washington of inanimate 
life has not yet been exploded. As a matter of fact, there is only one philosophical 
instrument capable of conveying more inaccurate impressions than the camera, and 
that is the gas-meter. Any one who is familiar with the actual structures of steel. 


* See Plates IX and X. 





728 


APPENDIX. 


and with the foggy series of photographs published from time to time to represent 
them, will admit the accuracy of the above statement. The technical difficulties in¬ 
volved in photographically reproducing the micro-structure of opaque objects under 
high powers are so great, that at present the only reliable means of reproduction is 
laborious hand-drawing, employing either a micrometer or camera lucida ; and the 
only reasonable objection to such a course is an imputation of malafides to the 
operator. 

For obvious reasons, the structure of iron and steel has herein received most 
attention; micrographic analysis is capable, however, of application to many alloys, 
and of explaining not only their mechanical properties, but also their electrical con¬ 
ductivities, so that the science is of importance, not only in practical metallurgy, 
but also in theoretical physics, based on observations of the electrical properties of 
alloys. 


II. Technical.* 

The study of this very important branch of steel metallurgy, initiated thirty years 
ago by Dr. Sorby, has attracted considerable attention on the Continent. In Ger¬ 
many, particularly, great strides have been made in its development under the 
superintendence of Professor Martens. By English metallurgists it has been until 
quite recently almost neglected, or condemned with faint praise. The mechanical dif¬ 
ficulties of preparing a perfect section and of delicately etching the surface, so as to 
reveal its true structure when examined with high powers as an opaque object, are con¬ 
siderable. The author has only overcome these obstacles after some years of laborious 
experiment, for which, however, he has been amply repaid by the discovery that the 
laws determining the structure of iron containing various percentages of carbon 
are fixed and concordant for given physical conditions; in fact, from puzzling chaos 
he has been enabled to evolve'order of a most interesting character, supplying, more¬ 
over, the key to the position he was attacking. 

i The Constituents of Iron and Carbon Steels. 

Pure Iron .—Perfectly pure iron is never met with in commercial masses, but in 
Swedish Lancashire hearth-rolled bars, containing in their average analysis 99.8 per 
cent of iron, groups of almost chemically pure crystals of the metal may be met with. 
They are readily distinguished by their well-defined facets and angles, and by the 
fact that they remain bright and smooth even after prolonged attacks by the exces¬ 
sively dilute nitric acid used for etching, which merely penetrates and makes visible 
the fine junction-lines of the crystals. In Fig. 686 is shown a micrometric reproduc¬ 
tion of crystals of pure iron viewed by direct illumination and magnified 600 diame¬ 
ters. Their geometric form agrees most nearly with that produced by interfering 
cubes and octahedra with dominant cubic faces.t It is, however, unusual to meet 
with such well-defined and geometrical crystals as those figured, because of the dis¬ 
tortion-stresses taking place in the metal during cooling after crystallization, which 
phenomenon the author’s experiments} indicate as occurring at a moderate red 
heat, the formation commencing at 750° C. and being completed at 720° C. 

Slightly Impure Iron .—In wrought iron and in mild steels the free iron crystals 
are often somewhat contaminated with a little residual carbon, which causes them 
during the process of etching to assume a pale-brown tint and a rough surface. The 
amount of carbon so involved is very small, seldom exceeding 0.05 per cent, and its 
mechanical influence is insensible. The author, therefore, will not at present 
further discriminate between the two kinds of iron crystals, though the exact nature 
of the carbide existing in the tinted crystals has some molecular interest in connec¬ 
tion with Osmond’s point A R 3. When very mild steels are submitted to prolonged 
heating in a vacuum at a temperature of 1400° C. and are then cooled in air, 
the microstructure of the steels undergoes a distinct change, in which the knots of 


* From Inst. Civ. Engrs ., vol. exxm. (1896), p. 137 et seq. 

t In a recent- communication to the Royal Society Mr. Thomas Andrews, F.R.S., has shown that 
in heavy slowly cooling masses of wrought iron the large primary crystals often split into numerous 
secondary cubes. 

X Journal of the Iron and Steel Institute , 1894. No. 1, p. 132 et seq. 




STUDY OF IRON AND STEEL BY MICRO GRAPHIC ANALYSIS • 729 


normal carbide of iron disappear and a large increase takes place in the number of 
tinted crystals. These facts are correlated thermally with a large permanent increase 
m the heat evolved at A R 3 on cooling, the carbon change-point almost disappearing 
at Ar 1 and its position at Ar 3 being raised about 10 0. These results are consis- 


Fig. 636.—Pure Iron Crystals Magnified 600 diameters. 



tent with the theory that there may exist traces of a carbide of iron intermediate in 
formula between the normal carbide Fe 3 C, and the all-important subcarbide to be 
presently described. 

Diffused Normal Carbide* —These areas, when the polished section is immersed 
in very dilute nitric acid, are at once partly covered with a dark-brown film of car¬ 
bonaceous coloring matter, the latter thus constituting an invaluable automatic 
staining medium. The dark areas, as will be shown subsequently, consist of iron 
containing about 13 per cent of normal carbide, Fe 3 C, diffused through its substance 
in the form of small, ill-defined plates and granules. They also mark the preliminary 
stage of formation of the ‘‘pearly constituent.” 

The Pearly Constituent.— This constituent is best developed in annealed steels, 
and presents the well-known hard and soft laminae discovered by Dr. Sorby. Jt has 
already been shown that the hard laminae are crystals of Fe 3 C. The soft interspaces 
are nearly pure iron. The parallel carbide plates may be wavy or straight, and they 
differ much in thickness and their distances apart. When the iron interspaces are 
very wide, the carbide plates are distinctly seen to be in relief, the fibres of the pol¬ 
ishing blocks having excavated the soft iron. Sections containing much “pearly con¬ 
stituent ” present on etching a beautiful play of pearly or opaline interference colors, 
which, if the etching is very light, are permanent. 

Crystallized Normal Carbide (Fe 3 C).—This substance, exclusive of its occurrence 
in the pearly constituent, may gather into large sectional rivers or into isolated 
masses. It requires then an experienced eye to distinguish it from perfectly pure 
iron, but, as a rule, the fact that it is always in relief and its brilliant silvery surface 
serve to identify it. 

Graphite. —This is Ledebur’s “ temper-carbon.” For English-speaking metallur- 


* These correspond with the “ amorphous iron ” of Dr. Muller. 











730 


APPENDIX. 


gists a more unfortunate name could hardly have been chosen. “ Annealing car¬ 
bon ” would have been better; but to make its nature quite clear the author will 
throughout this paper employ the name graphite, as expressing for all practical 
purposes what the substance is. In steel it occurs in the form of dark rounded 
dots (or more rarely in short, worm-like masses) well defined against a background 
of pale iron. 

Snbcarbide of Iron (or (5 iron).—But one more constituent remains to be de¬ 
scribed, and this, if Mr. Osmond’s theory be true, must be (S iron charged with dis¬ 
solved carbon. On lightly etching a polished section consisting mainly of this 
compound it retains its polish but assumes a “ black-leaded ” appearance, due to a 
very faint coating of dark carbonaceous matter. It seems homogeneous and appar¬ 
ently non-crystalline, but probably consists of minute crystals, the junction-lines of 
which are beyond the range of microscopic vision or are obscured by the faint car¬ 
bonaceous deposit. When deeply etched, this substance becomes covered with a 
velvet black deposit, which may be removed by the finger, staining the latter. The 
body just described is found only in hardened or hardened-and-tempered steel. The 
author will presently produce whats eems to him conclusive microscopical thermal 
•and magnetic evidence that this substance is not an allotropic modification of iron, 
but a definite though remarkably attenuated and unstable carbide of iron of intense 
hardness, and corresponding with the formula Fe 2 4 C. 


Details of Microscopic Observations. 

The structures illustrated, Plates VII and VIII, were all drawn from the micro¬ 
scope, when necessary a micrometer being used on correspondingly graduated circles 
28 inches in diameter. The drawings were then reduced by photography to the 
•diameter of the microscopic field. The labor involved in carrying out this process 
was great, but the results depict the structures with an accuracy unattainable by 
direct photography. Direct illumination was employed throughout. 

Normal Steel No. 1 , PI. YII (Carbon 0.08 per cent).—The structure consists of 
irregular crystals of iron, amongst which are sparingly distributed small dark knots 
of the diffused normal carbide areas. On comparing this section with that of the 
pure iron, it will be seen that the presence of even 0.08 per cent of carbon is at 
■once decisively revealed by the microscope. 

Annealed Steel No. 1 f (Carbon 0.08 per cent).—The effect of annealing had been 
to produce a distinct increase in the size and geometry of the iron crystals, and to 
gather the Fe 3 C, diffused through the dark normal areas, into isolated patches of 
coarse pearly constituent surrounded by thick sectional meshes of crystallized Fe 3 C. 

Normal and Annealed Steels , No. H (Carbon 0.21 per cent).—These sections 
were in all respects intermediate between those of steels Nos. 1 and 2. It was not 
therefore deemed necessary to illustrate them. 

Normal Steel , No. 2, PI. YII (Carbon 0.38 per cent).—This section consists of a 
mixture of crystals of iron, and large irregular dark areas of diffused normal carbide, 
the latter occupying on an average nearly half the field. 

Annealed Steel , No. 2 PI. VII (Carbon 0.38 per cent).—On annealing, the iron 
crystals have become larger and more definite, whilst the dark areas have aggregated; 
and on cooling the components have segregated, forming striae of crystallized ^ Fe 3 C, , 
divided by spaces of iron. The groups of striae are often partly surrounded by sec¬ 
tional meshes of Fe 3 C, a few isolated striae of which compound may be sometimes 
observed between the junctions of the iron crystals. 

Annealed Steel. No. 2 t (Carbon 0.38 per cent).—This section gives a general 
view of the structure over a comparatively large area. It forms a beautiful micro¬ 
scopic object resembling an irregular mosaic pavement composed of white crystals 
of iron and large irregular patches of the pearly constituent, showing splendid ‘inter¬ 
ference colors. Of course a magnification of 100 times a linear dimension is insuffi¬ 
cient to resolve the striae of the pearly constituent. 


* I" examining the engravings of the sections a lens will be found useful for some of the finer 
structures 

+ Tiiis figure is given m the author’s plate, but was not reproduced for this work —J B J 





PLATE YU. 



Microscopic Sections of Steel, magnified 500 diameters. Treatment and per cent carbon indicated. 
Drawn by Prof. J. O. Arnold. (Inst. Civ. Engrs., vol. cxxm. (1896) 11. 4.) 










































. 

' k’t* 














PLATE VIII. 




No. 6. ' 

Annealed 


No. 4. v 
Annealed 


1.47 C 


0.89 C, 




: 

k 

\ 

\ 

\ 

\ 

\ : 
V 

x 

No. 4. 

Hardened. <<; 


No. 6. ^ 
Hardened, 


0.89 C, 


1.47 C, 


Microscopic Sections of Steel, magnified 500 diameters. Treatment and per cent carbon indicated. 
Drawn by Prof. J. O. Arnold. {Inst. Civ. Engrs., vol. cxxiii. (189G) PI. 4.) 

























STUDY OF IRON AND STEEL BY MICROGRAPHIC ANALYSIS. 731 


The General Influence of Annealing on Mild Cast Steel. 

As No. 2 steel contains about the same percentage of carbon as that contained in 
liigh-class castings, it will be well to discuss in connection with it the general prin¬ 
ciples underlying the operation of flame annealing. The surface oxidation of carbon 
resulting from this process will be neglected, as its effect is comparatively small, 
and only the action of annealing on the main portion of the steel which is unaltered 
in ultimate chemical composition will be considered. 

1 he ideas prevalent among metallurgists on this subject are often very erroneous. 
It has been stated, both in text-books and in practical papers, that the action of 
annealing is to produce smaller crystals. As a matter of fact, the crystals of an 
annealed steel are always larger than those existing in the metal before annealing. 
The idea of smaller crystals has doubtless arisen from a confusion of effect with 
cause. After annealing, the crystals of the fractured metal do appear to the eye 
smaller than those in the original material; but the reason for this is found in the 
fact that during the process of rupture they elongate, what are really seen being 
the ends of the ductile, and consequently drawn out, crystals, and not (as in the 
•case of the comparatively brittle unannealed metal) the originally existing facets. 
Also, frequently, what are regarded as crystals in the fracture of a brittle unan¬ 
nealed steel casting are really groups containing many crystals, originally bounded 
by lines of great intercrystalline weakness, along which rupture has naturally taken 
place. As a rule, the fracture of steel bears little or no relation to its true micro- 
structure. It has also been stated that on annealing, the iron and the pearly constit¬ 
uent become more intimately mixed ; for which Dr. Sorby has been quoted as the au¬ 
thority. Dr. Sorby’s general conclusion on this matter was accurate, and was exactly 
opposite to that attributed to him. The mistake seems to have arisen from an 
imperfect knowledge of the meaning of the word “segregate.” The true action of 
annealing on a moderately mild steel, containing, say, 0.35 per cent of carbon, is as 
follows: 1. The comparatively small and distorted crystals of the original metal 
become larger and more geometrical in form (they are therefore freer from internal 
stresses), and the intercrystalline cohesion, if originally weak, is much strength¬ 
ened.* 2. The carbonized areas existing in the unannealed steel, chiefly in irregular 
elongated masses, gather together during the slow cooling into rounded or harp¬ 
shaped areas, in which form they favor the continuity of the iron crystals to a much 
greater extent than the original arrangement. 3. The rounded or harp-shaped 
areas, into which are concentrated the normal carbide of iron split up during the 
slow cooling into plates of crystallized Fe 3 C, separated by large interspaces of iron; 
hence the latter become dovetailed into the main body of the iron crystals. This 
continuity, however, is not perfect, being frequently broken by the sectional meshes 
partly environing the laminated areas. Thus long lines formed by a juxtaposition 
of two distinct constituents are broken up, and the iron becomes almost continuous 
throughout. In fact, the carbon is concentrated into small plates suspended in the 
iron, mixed with only about 5 per cent of the total metal instead of being dis¬ 
tributed in large more or less continuous areas forming about 40 per cent of the 
mass. The foregoing statements are common to the cases of forged steel, as well as 
of the metal as cast, but they apply with peculiar force to the last-mentioned mate¬ 
rial, in which the intercrystalline cohesion is usually weak; which is not often the 
case in forged steels, because the work put upon the material has already repaired 
the faulty crystal-junctions in a manner analogous to the influence exercised by 
annealing.! 

In order to render the above facts more clear, half-fields of No. 2 steel in the 
annealed and normal conditions are exemplified in Fig. 14.J The sections from 
which these were drawn were very lightly etched so as to bring out only the car¬ 
bonized constituents without developing the lines marking the intercrystalline junc- 


* Perfect, intercrystalline cohesion is synonymous with that hitherto mysterious essence known to 

the practical man as “ body.” . . . , .. „ „ . 

+ The question of the influence of annealing on the various types of steel castings is of sufficient 
importance to warrant its special consideration in a separate paper, for which the author has for 
some time past been collecting data, some of which are of a startling nature. 

X Not reproduced here. 








732 


APPENDIX. 


tions. The several sections of No. 2 steel show clearly tnat existing views as to 
steel being built up of a series of cemented cells are erroneous. As already stated, 
streaks of carbide cement may now and then be seen between the junctions of the 
iron crystals, but such constitute incidents, and not a principle. As a matter of 
fact, if the facets of the iron crystals were really united by Fe 3 C cement, a mild 
steel would be easily fractured by a blow from a heavy sledge-hammer. The 
author, from the results of many experiments, confidently makes the following 
statement: 

If the cohesive force acting between the facets of crystals is from any chemical, 
thermal, or mechanical cause seriously weakened, the metal will appear to be very 
brittle, owing to rupture under the influence of a sudden shock occurring along the 
weak junction-lines, in spite of the fact that the molecular cohesion may be perfect 
and the individual crystals ductile.* 

From the foregoing statement it will be obvious that a metal may be soft to the 
drill or under compression, and yet brittle under impact, exhibiting little or no 
ductility in tension. It is also clear that in such a case chemical analysis is useless. 
The author, however, is not yet prepared to state the exact means by which inter¬ 
crystalline weakness may be measured by the microscope, but he is hopeful that in 
the near future such measurements may be possible. That in nearly pure iron the 
intercrystalline cohesion and the molecular cohesion may be equal, is proved by the 
tensile test of No. 1 steel annealed. This metal is composed of large definite crys¬ 
tals, yet the elongation was 53 per cent and the reduction of area at the point of 
fracture in tension was 77 per cent. 

Normal Steel No. 3, PI. VII (Carbon 0.59 per cent).—In this section the dark nor¬ 
mal carbide areas considerably exceed the now isolated and highly distorted crystals 
of iron. 

Annealed Steel No. 3, PI. YII (Carbon 0.59 per cent).—This section confirms, and 
presents on a larger scale than No. 2 steel annealed, the breaking up of the dark 
areas into stride of crystallized Fe 3 C separated by interspaces of iron. 

Steel No. 3^ (Carbon 0.74 per cent). Slightly annealed.—This section was in all 
respects intermediate to the normal sections of steels Nos. 3 and 4, containing fewer 
iron patches than the former. 

Normal Steel No. 4, PI. VIII (Carbon 0.89 per cent).—This section presents a 
feature of vital importance in connection with the theory of steel which the author 
will presently enunciate. The entire structure consists of ill-defined crystals forming 
dark areas of iron containing suspended normal carbide, whilst crystals of iron free 
from suspended carbide have necessarily altogether disappeared. In other words, 
iron containing 0.89 per cent of carbon presents a critical microscopical point which 
will be hereinafter referred to as the “ saturation-point steels in which the carbon 
falls below 0.89 per cent will be termed “ unsaturated ”; whilst steels containing more 
than 0.89 per cent carbon will be distinguished as “ supersaturated,” for reasons to 
be presently stated. 

Annealed Steel No. 4, PI. VIII (Carbon 0.89 per cent).—This section consists entirely 
of crystals of the pearly constituent. The crystallized striae of Fe 3 C are in nearly 
parallel lines, some straight, others wavy. Small isolated masses of this compound 
also occur sparingly. The thickness of the plates and of the iron interspaces vary 
considerably. In one area the hard plates are in such relief owing to the wearing 
away of the broad, soft iron interspaces, that they actually cast microscopic shadows, 
as indicated in the figure. The microsection of this steel, consisting entirely of the 
pearly constituent, presents to the eye a beautiful play of colors resembling those of 
mother-of-pearl. 

Normal Steel No. 5,t (Carbon 1.2 per cent).—The main portion of this section 
is similar to that of normal steel No. 4, but each crystal or group of crystals is 

* Purely scientific investigators dealing with the physics of iron discourse freely on molecules and 
their distances, but they ignore crystals and their comparatively huge interspaces. This is a grave 
error; e g., there is little doubt that magnetic properties are much influenced by the dimensions of 
the crystals into which the molecules are grouped The author emphatically reiterates that deduc¬ 
tions explaining observed mechanical facts on the basis of allotropic changes in the molecular hi chi 
tectures of metals are valueless, unless the effects due to crystalline architecture have been previously 
determined and allowed for. The effects due to tne first-mentioned cause are often very small in 
Comparison with the effects produced by intercrystalliue causes. J 

t Not reproduced here. 




STUDY OF IRON AND STEEL BY MI GROG RA PIJIO ANALYSIS. 733 


surrounded by a sectional mesh of Fe 3 C. Isolated striae of the latter compound also 
occur. It must be remembered that the strings of carbide which appear sectionally 
as a coarse and irregular network are in reality, when translated into the solid, more 
or less perfect investing membranes. This statement is proved by the fact that both 
transverse and longitudinal sections present the same characteristics. 

Annealed Steel No. 5,* (Combined Carbon 0.92 per cent, Graphite 0.28 per 
cent).—This section possesses features of special interest. It presents two distinct 
types of field, which are reproduced in two half-fields. In one will be observed crys¬ 
tals or groups of crystals composed of the pearly constituent enclosed in very large 
sectional meshes of Fe 3 C. These thick membranes have evidently resulted from a 
confluence, during the slow cooling, of the comparatively small membranes present 
in the normal steel. In parts of the section from which meshes are absent there are, 
however, round almost black patches of graphite, set for the most partin the centres 
of round patches of bright iron, the remainder of such field being as usual composed 
of the pearly constituent. It would therefore appear that when the mobilized masses 
of carbide attain a certain magnitude, they act during the slow cooling like very 
highly carbonized while pig-iron, dissociating into nearly pure iron and graphite. 
The temperature at which this separation takes place will be considered in connec¬ 
tion with the annealed sample of No. G steel. 

Normal Steel No. 6 , PI. VIII (Carbon 1.47 per cent).—In this section the dark 
background of iron permeated with diffused Fe 3 C is much broken up by thick irreg¬ 
ular meshes of crystallized Fe s C. The enclosed crystals also contain large fern-like 
streaks of the crystallized carbide, the whole constituting a beautiful and striking 
microscopic object. 

Annealed Steel No. 6 , PI. VIII (Combined Carbon 0.33 per cent, Graphite i.l4 per 
cent).—In this section about one third of the area consists of the pearly constituent, 
the other two thirds being composed of iron crystals largely spotted with dark round 
patches, and short wonn-like masses of graphite. The latter must have separated 
below the temperature of the carbon change point Ar 1, which is about 685° C., be¬ 
cause the large masses of carbide described in connection with annealed steel No. 5 
would in the present case be still greater; and not only have they become totally de¬ 
composed, but have evidently also gathered in much of the carbide existing as small 
plates in the pearly constituent. Hence, as the plates so collected would not have 
crystallized till the temperature had fallen to about 680° C., it appears certain that 
the decomposition of the Fe 3 C into iron and graphite must take place at or below 
Ar 1 i.e., at a low red heat. The interesting fact, that this dissociation is facilitated 
by pressure is proved by the investigations of Mr. B. W. Winder, who found that 
hard file-steel leaving the rolls at a low red heat almost invariably contained graph¬ 
ite in large quantities, whilst similar steel finished at a fair red heat was almost de¬ 
void of free carbon. 

Annealed Steel No. 6,* (Combined Carbon 0.33 percent, Graphite 1.14 per cent).— 
This section presents a large area of the graphitic metal, showing the crystals of 
iron, the spots of graphite, and the curiously irregular masses of the pearly con¬ 
stituent in which is contained the 0.33 per cent of combined carbon present. At 100 
diameters the microscope is of course incapable of resolving the striae of the pearly 
constituent, which, however, presents a play of gorgeous colors. From the three 
graphitic sections referred to, it will be seen that supersaturated steels are always 
very liable to deposit graphite on annealing. Such a phenomenon is seldom or never 
observed on or below the saturation-point. 

The foregoing microscopical facts have been known to the author for about three 
years, having been ascertained by an examination of another series of steels similar 
to those now°under consideration. But as it was unexpectedly found that the harder 
steels contained about 0.3 per cent of manganese, the author rejected the first series, 
and made a purer set of steels upon which to commence the research afresh. As the 
result proved, the comparatively high manganese in the hard steels did not seriously 
affect the results just described, and the first series now constitute confirmatory 
evidence, which has also been augmented by the examination of many samples of 
commercial steels. 


* Not reproduced. 







734 


APPENDIX. 


General Theory Based on the Microscopical liesnits. 

The evidence given by the microstructure of the steels is thus interpreted by the 
author: 

1. The sharply defined localization of the areas containing respectively the dif¬ 
fused normal and crystallized carbides,(until the saturation-point at 0.89 per cent of 
carbon is reached) seems to confirm beyond doubt the accuracy of the general con¬ 
clusion of Dr. Sorby—that at high temperatures a compound of iron and carbon 
exists, which on cooling splits into iron and an intensely hard compound very rich 
in carbon. 

2. The fact that the dark carbonized areas of normal steels increase proportion¬ 
ally to the carbon until the saturation-point is reached seems quite incompatible 
with the theory that at a high temperature the carbon is in a free state in mere 
solution. Under such conditions the carbide of iron would be evenly diffused after 
its deposition in situ on cooling, and would on etching yield an almost homogeneous 
microscopic field, darkening in color as the carbon increased ; inasmuch as the 
stronger the solution at high temperatures, the greater the amount of diffused carbide 
in the cold metal, and, cceteris paribus, the thicker the deposit of carbonaceous col¬ 
oring matter released on the surface of the etched section. 

If it be admitted that the dark areas in normal steels and the striated areas in 
the corresponding annealed metals are mixtures resulting from the decomposition of 
a compound existing at temperatures above the change-point A R 1, it necessarily fol¬ 
lows that at the saturation-point (at 0.89 per cent of carbon) the whole mass of the 
iron is at a full red heat in combination with the carbon, and hence that the percent¬ 
age of carbon in the saturated steel is also the percentage of carbon in the formula 
of the compound. Therefore the compound will contain 0.89 per cent of carbon 
and 99.11 per cent of iron, corresponding with the formula Fe 2 4 C, which requires 
0.884 per cent of carbon. 

In the case of a supersaturated steel made by gradually adding, say 1.5, per cent 
of carbon to pure iron in a molten state: when the iron has combined with 0.89 per 
cent of carbon it will have been converted into a carbide of formula Fe 2 4 C ; but on 
adding more carbon a portion of the subcarbide will be carbonized to the normal 
carbide Fe 3 C ; thus- 

Fe 24 C + 7C = 8Fe 3 C. 


• 

The molten mass then consists of a mixture of the normal carbide with subcar¬ 
bide of iron. On cooling, the subcarbide decomposes into ill-defined crystals of 
iron permeated with diffused Fe 3 C, whilst the surplus normal carbide is thrown off 
in the form of membranes enveloping the irregular crystals of the mixture resulting 
from the decomposition of the subcarbide. 

The Structure of Hardened Steels. 

To obtain more conclusive microscopic evidence of the accuracy of the theory just 
■enunciated, it was obviously necessary to determine the structure* of hardened steel 
below, on, and above the saturation-point. When it is remembered that even the 
skill of Dr. Sorby was baffled in all his efforts to obtain satisfactory sections of hard¬ 
ened steel, it is not surprising that, although possessing superior appliances, the 
author’s experiments in this direction were for several years almost fruitless, yield¬ 
ing most puzzling and erratic results. However, comparatively recently, the author 
possessed himself of the key to the position, in the fact that it was absolutely neces¬ 
sary to harden the samples from a nearly white heat, without allowing them to come 
into contact with either air or water. This was because the decarbonizing action of 
a film of magnetic oxide on the surface of a piece at a full red heat extended irregu¬ 
larly to such a depth that it was almost impossible in the flint hard steels to grind 
off the partially decarbonized surfaces without disturbing the structure or “lettino- 
down ” the steel. This fatal defect was finally removed by the following simple 
though somewhat costly plan. Each microsection was polished and encased air-tight 
in thin plates of the same steel in the manner indicated in Fig. 637. The encased 
mierosection was then slowly heated to about 1050° C., and was quenched with the 


STUDY OF IRON AND STEEL BY MICROGRAPIIIC ANALYSIS. 735 


greatest possible rapidity in a large tank of ice-cold water. On drying and removing 
the casings the section, although it had been heated during half an hour up to an 


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incipient white heat, was found to be quite bright and absolutely unoxidized on the 
tower polished face. On lightly etching three typical sections the following results 
were obtained: 

Hardened Steel , No. 2, PI. VII (Carbon 0.38 per cent).—On being etched, the 
sample assumed a roughish texture and a dull, somewhat dark-gray tint. ’ On 
lightly removing the gray deposit the steel was found to consist of two distinct con¬ 
stituents, viz., free iron and an amorphous substance to which the acid had commu¬ 
nicated a dark color. In some fields the iron, and in others the dark constituent 
predominated. The author affirms the latter to be subcarbide of iron. The section 
figured represents an average field. The shock of the sudden cooling seems to have 
dispersed the iron through the dark substance in masses irregular in size and fan¬ 
tastic in shape—many particles, no doubt, being too small for separate microscopic 
definition. 

Hardened Steel , No. 4, PI. VIII (Carbon 0.89 per cent).—This section, on being 
very lightly etched, retained its polish, but assumed a “ blackleaded ” appearance. 
When examined under the microscope the field at first sight presented a brownish- 
colored blank, in which no crystalline structure could be detected. A prolonged 
and careful examination showed that the section really possessed an indefinite 
granular roughness, but no crystalline junctions could be detected. It is, however, 
probable that the mass really consists of minute crystals, the boundary-lines of 
which are beyond the reach of microscopic vision or are rendered indefinable by the 
faint carbonaceous deposit. This is the only practically homogeneous section the 
author has ever obtained during many years of close study of the microstructure 
of steel and iron. 

Hardened Steel , No. 6, PI. VIII (Carbon 1.47 per cent).—On being etched, this 
section behaved in every respect like hardened steel No. 4. The groundwork of the 
section was also found to be identical with the saturated metal, but all over it was 
spread a network of fine meshes, together with isolated striae and irregular dots of 
a substance microscopically corresponding in all respects to Fe 3 C. 

Thus the microstructures of the hardened steels seem in accordance with the 
author’s theory. The unsaturated steel possesses a structure such as might be ex¬ 
pected from a suddenly quenched mixture of free iron and subcarbide of iron.* 
The saturated steel fulfils the necessary theoretical condition of homogeneity, wdiilst 
the supersaturated steel decidedly reveals the presence of surplus meshes of normal 
carbide of iron. 

* The non-homogeneous nature of hardened unsaturated steel is best seen in oil-quenched gun- 
steel containing about 0.3 per cent of carbon, the almost black subcarbide areas being fantastically- 
enmeshed in free iron. 












736 


APPENDIX . 


the supersaturated steel decidedly reveals the presence of surplus meshes of normal 
carbide of iron. 


Note by the Author. 

Photomicrographs of Steel .—The microscopic sections shown in Plates VII and 
VIII are from drawings. Those shown in Plates IX, X, and XI are reproduced 
photographs, taken directly from the specimen, and they reveal these just as they 
would appear to the observer, so far as can be done by photography. The drawings 
indicate the crystalline arrangement much better than the photographs, but reliance 
must be placed in the competency and faithfulness of the draughtsman, who is of 
course the observer. With the photographs the personal equation of the observer 
is eliminated. The two taken together reveal, to some extent, the merits and the 
possibilities of this method of analysis. Each of these methods of illustration has 
its advocates, the chief of whom to-day are perhaps the respective authorities, 
here quoted—Arnold and Martens. 



APPENDIX C. 


P 


COMPARATIVE ANALYSIS OF THE RESOLUTIONS OF THE CONVENTIONS 
OF MUNICH, DRESDEN, BERLIN, AND VIENNA, AND THE RECOM¬ 
MENDATIONS OF THE AMERICAN SOCIETY OF MECHANICAL ENGI¬ 
NEERS, WITH THE CONCLUSIONS ADOPTED BY THE FRENCH COM¬ 
MISSION IN REFERENCE TO THE TESTING OF METALS, 

By Mr. L. Bacltc, 

Member of the French Commission on Methods of Testing the Materials of Construction. 

Translated by O. M, Carter, Capt. Corps of Engrs. U. S. A., and 
E. A. Gieseler, U. S. Asst. Engr. 

INTRODUCTION. 

Two attempts have been made abroad to secure the adoption of uniform methods 
of testing construction materials—one under the auspices of technical conventions 
held at different times in Munich, Dresden, Berlin, and Vienna, where, besides the 
German members, there were present delegates representing various foreign coun¬ 
tries; the other, in America, under the auspices of the American Society of Mechan¬ 
ical Engineers. Two reports presented to the Committee of Research, one by M. 
Polonceau and the other by M. Bade, have given translations of the conclusions and 
recommendations thus adopted by the Conventions and by the American Society. 

It is proper, therefore, to make a comparison between the resolutions adopted by 
foreign conventions and those adopted by our own commission, in order that we may 
examine the differences and analogies which they present. Such a comparison affords 
an opportunity of deciding whether there should be renewed study and research upon 
the points of difference, and of determining whether we may hope for international 
unity in the future, based upon the common resolutions already recommended and 
even now adopted in the current practical domestic relations of different countries. 

The work of comparison in the present report, intended in some measure to form 
a starting-point for the studies of an international commission which might be crea¬ 
ted for this purpose, has been confined to the methods of testing metals, which is 
the sole subject of discussion in Section A. (Section des Metaux.) 

To facilitate comparison, avoiding as much as possible all omissions, an attempt 
has been made to place together all resolutions relating to the same subject, and to 
this end the methods of classification used in our General Report have been adopted. 
The present report follows, therefore, the divisions and rules of the General Report, 
giving under each chapter only such resolutions as offer a possibility of comparison 
with the corresponding foreign recommendations. 

The comparison is usually made by referring to the resolutionsof the Conventions, 
for those are frequently reproduced in the recommendations of the American Society. 
In certain cases, however, those two groups of resolutions piesent differences which 

then become the subject of special mention. 

It is advisable to point out in a general way, among the resolutions to be com¬ 
pared a primary difference in principle (which is, however, of little importance) re- 

73? 


738 


APPENDIX. 


lating to tests made upon finished pieces. The resolutions of the Conventions, iden¬ 
tical in this respect with the resolutions of the American Society, define the tests 
which should be made upon certain articles in current use, such as tires, axles, and 
rails. For certain kinds of metals, such as wrought or cast iron, for different speci¬ 
fied uses, they advise the discarding of such tests as to them seem unnecessary, while 
our Commission refuses to make any such elimination, feeling totally unauthorized 
to do so. 

With regard especially to methods of testing, the studies of our Commission have 
been more general than those made abroad, and the recommendations that we have 
made include various kinds of tests not mentioned in the foreign resolutions, with 
which, therefore, no comparison is possible. 

On the other hand, certain methods of testing have been especially recommended 
in all of the resolutions, such as tensile, shock, and bending tests, and it is with re¬ 
spect to those that the committee should make special comparative examinations. 

In tensile tests the Conventions do not define so definitely as do we the quantities 
to be measured; they do not give the same limits of approximation in their meas¬ 
ures; they follow the law of similarity in adopting cylindrical test-pieces, but use a 
different coefficient from ours, which tends to give to the useful or test length a 
greater value for the same diameter. Other differences are apparent in the descrip¬ 
tion of their standard rectangular test-pieces. 

The American Society prescribes an invariable standard of test length, indepen¬ 
dent of both the diameter and the cross-section of the test-piece. 

The resolutions of the Conventions concerning shock tests are confined almost 
entirely to finished pieces. They give more explicit directions than do we in regard 
to the arrangement of the apparatus employed, but certain experiments made upon 
test-pieces that we have especially studied are not mentioned by them. 

In bending tests they recommend that the bending should be done around a 
mandrel of unvarying diameter, while the American Society claims that the mandrel 
should vary in proportion to the thickness of the test-piece. The dimensions of 
their bars differ also from those used by us. 

The differences just given are the most marked ; but they are in reality of little 
importance, and probably can be easily overcome. 

In the general resolutions concerning the precautions to be observed in preparing 
test-pieces we find at. times differences of detail, but they are usually cf minor 
importance, since the three sets of resolutions upon that subject are inspired by the 
same general principles. 

In so far as the general formulas, as well as the methods of testing referred to 
above, are concerned, we find as a result of this comparison nothing to indicate that 
the desired unity of method may not be attained should an international commission 
be called for that purpose. 


FIRST AND SECOND PARTS. 

PHYSICAL EXAMINATION AND CHEMICAL TESTS. 

The resolutions of the Conventions do not contain any specific directions upon 
those subjects, but they advise the acquisition of as thorough a knowledge as possi¬ 
ble of the results of both microscopic and chemical examinations, especially in all 
cases of scientific research. 

According to the recommendations of the American Society, the magnetic condi¬ 
tion of a metal should be especially mentioned. 

Those recommendations require, moreover, that when in tensile tests the rup¬ 
tured section presents a cupel form the fact should be mentioned, the relative posi¬ 
tion of the edges of the cupels with reference to each of the pieces of the tested bar 
being indicated. 

To determine the effects of tempering upon steel, the American Society recom¬ 
mends in addition that the bars should be heated to a bright red and immediately 
quenched in water at from 32° to 40° F. (0° to 5° C.) 

Our Commission requires that the test-bars should be heated to a comparatively 
deep cherry-red and quenched in water at 28° C., the volume of water being great 
in proportion to the volume of the bars. 


UNIFORM METHODS OF TESTING METALS. 


739 

The resolutions of the Conventions also require that the metal should be heated 
to a cherry-red (placed by them at from 550° to 600° C.) and quenched in water at - 
25° C. 

They recommend also, as will be seen later on, that copper test-pieces should be 
heated to 700° C. and quenched in water at 15° C. 

That recommendation is not found among our conclusions, which require, how¬ 
ever, that deductions from experiments with copper or its alloys shall be drawn 
from tests made after the last annealing in the manufacture of the plates. 

THIRD PART. 

MECHANICAL TESTS.—RECOMMENDATIONS COMMON TO ALL METHODS OF TESTING. 

Chapter I.*—General Observations. 

Our resolutions show the importance of accompanying mechanical tests of what¬ 
ever nature with the tensile test ; they indicate the approximate exactitude with 
which one should be content in the majority of current tests, by showing that in 
practical experiments the exaggerated precision required in scientific research is not 
necessary. They avoid, moreover, giving any indication regarding a choice between 
the various methods of testing according to the application proposed. 

The resolutions of the Conventions recommend generally that testing should be 
done with reference to the work to which the pieces are to be subjected ; at the 
same time they indicate which test to adopt and which to reject in specified cases ; 
they advise the adoption of regular tests for certain pieces frequently employed, 
such as rails, tires, and axles for railroad use, cast or wrought iron, materials for 
shipbuilding, etc., recommending the greatest possible number of tests upon all 
pieces of the same delivery, testing without damaging them. 

They recommend, for instance, testing tires and axles by shock with a standard 
impact machine, claiming that it is useless to test tires by a hand-hammer or axles 
by flexure. They add that it may be advisable to have recourse to tensile tests to 
obtain certain additional complemental information. 

They confine themselves to recommending that the degree of exactitude attained 
in the tests should be stated, or at least that data should be furnished allowing it to 
be determined. 

The resolutions of the American Society recommend that tests should be made as 
far as possible upon the pieces themselves whose quality it is desired to ascertain, 
being careful to reproduce as far as possible the conditions to which the pieces will 
be subjected when in use. They add, with a view to facilitate comparison, that it 
would be well to make a standard test over and above the tests upon finished pieces. 

With regard to registering apparatus, our Commission limits itself to saying 
that it should be employed without hesitation, as its use even when it is not posi¬ 
tively accurate may prevent serious error. 

The American Society seems, however, to recommend it more formally, especially 
for tensile tests. 

In regard to test-pieces that are imperfect, our resolutions require that they 
shall be thrown out of the calculation of averages established from a scientific point 
of view whenever there are exceptional or local defects in the test-pieces. 

The American Society remarks on this subject that in making tests all pieces of 
abnormal appearance or those showing superficial defects should be rejected. If, how¬ 
ever, a perfect piece cannot be found, a record of the imperfections should be kept. 

Chapter II. —Preparation of Test-pieces. 

CONDITION OF THE METAL. 

Our resolutions recommend in general that the condition of the metal employed 
shall be precisely defined principally with respect to hammer-hardening (ecrouissage ),t 


* The “ chapter* ” here referred to are tlie chapters of Part Three (Vol. I) containing the recom¬ 
mendations of the French Commission in reference to the Testing of Metals. 

t Hummer or cold hardening’ (ecrouissage) is an alteration produced hy working a m^tal w!u>n coM 
with a hammer, a die, a punch, shears, etc. Ecrouissage is the standard change in a metal which has 
been subjected to a permanent deformation at a temperature lower than that required for annealing. 





740 


APPENDIX. 


and especially when soft metals are used, that the test-pieces shall not be removed 
* until the metal has been brought to the exact condition under which it is decided to 
test it; they mention also the precautions to be taken in finishing off test-pieces, in 
order to avoid any strain which might produce a change in the condition of the 
metal. 

The American Society also insists upon the importance of observing its resolutions, 
which state that the lightest blow from a hammer, or any blow incorrectly given, 
may falsify results, should the abnormal strain thus produced be greater than that 
required to cause variation in the quality of the metal to be tested. 

They admit, moreover, that soft metals are less susceptible to those influences 
than hard metals. 

With regard to plates of mild steel, the Conventions have decided that it is 
unnecessary to test them after they have been annealed, as it is too difficult to deter¬ 
mine the exact temperature of annealing. They add, in conclusion, and in accord 
with our Commission, that the object generally sought is to ascertain the nature of 
the metal in the condition when delivered. 

THE PLACE AT WHICH AND THE MANNER IN W T HICH TEST-PIECES SHOULD BE CUT.— 

FABRICATION OF TEST-BARS. 

The resolutions of the Conventions require, for instance, with rails, that the bars 
detached shall have square* sections and contain the exterior fibres of the rail. Our 
advice is in general to take the test-bars from the thinnest and thickest parts of the 
final rolled section. 

With regard to plates, the resolutions of the Conventions are imbued with the 
same spirit as ours, from which they vary only in minor details. They advise taking 
the test-pieces from the longitudinal and transverse sides, cutting away, when raw 
or uncut plates are used, at least 30 millimeters in width from the exterior ; when 
dressed plates are used the test-pieces should be chosen from plane plates of regular 
thickness. 

They admit, without going further into details, that the strips should be cut with 
shears or by a saw, but for bridge iron or boiler-plates they require that the strips 
cut off by shears shall be straightened out cold by a press, by the use of a wooden 
mallet, or by small hammers of lead or copper. Before cutting out the test-pieces 
the strips should be planed down on each side for a width of at least 5 millimeters 
to do away with the effect of the shears. Upon express demand annealing is per- 
milted for straightening out strips cut by shears from boiler-plates. 

Our resolutions impose more minute precautions to prevent the deformation of 
the bars, and if annealing is indispensable for straightening, they require that a 
temperature of 700° C. shall not. be exceeded. 

They require also that the test-pieces shall be cut from the strips by a machine, 
without, however, stipulating that a depth of 5 millimeters in thickness of the metal 
shall be removed. 

For rolled products, the resolutions of the Conventions prescribe that the rough- 
rolled surfaces shall be preserved. Our instructions do not mention that point, but 
it may be observed that in practice that method is always followed. 

The Conventions require, finally, that the reports of tests shall make known the 
source and the method of manufacture of the test-pieces, and they add that those 
pieces designed for compression tests should, as far as possible, be smoothed by 
planing or turning. 

In the preparation of test-pieces of copper, they recommend the most minute 
precautions, which are also mentioned in our resolutions. 

Besides those, they add, as has been indicated above, that bars of copper should 
be annealed at 700° C.t before they are completed, then cooled in the air to a dull 
red, and finally quenched in water at 15° C., while our resolutions demand that tests 
shall be made after the last annealing in the fabrication of the plates. 

In regard to test-pieces of cast iron, the Conventions require that they shall be 
cast in a mould of very dry sand having an inclination of 10 centimeters per meter. 


* The original resolutions require only a rectangular section.—O. M. C. 
t That temperature must not be exceeded. See Original Resolutions.—O. M. C. 



UNIFORM METHODS OF TESTING METALS. 


741 


The entrance for the flow of the melted material should be placed 20 centimeters 
above the mould, determining thus the length of the runner-stick. Those test-pieces 
should be left with the rough surfaces produced by the moulds. 

Our resolutions require that for pieces which at some places are more than 9 
centimeters thick the test-bars should be cut by a machine from the foot of the 
runner-stick. For other pieces the test-bars may be cast separately, if care be taken 
to give the mould an inclination of about 20 centimeters per meter and to make the 
runner-stick from 15 to 20 centimeters long. 

They always discard the runner-stick for bars cast in contiguous pieces. 

1 he American Society remarks, without stating any general laws, that the super¬ 
ficial crust found upon raw materials, either rolled or cast, is either an advantage or 
a hindrance, according to the work in view, and should therefore be taken into ac¬ 
count in the preparation of test-pieces. 

Chapter III.— Study of the Influence of Temperature upon the 

Results of Tests. 

Our resolutions point out the precautions to be observed in making tests at any 
given temperature, high or low; afterwards they deal especially with tests made at 
ordinary temperatures, remarking that the influence of variations in temperature is 
felt principally in shock tests, and giving directions for the mitigation of the same. 

The resolutions of the Conventions do not contain any directions with regard to 
those tests; they require that in the cold bending of copper bars the temperature 
shall not be less than 10° C. 

Chapter IV. —Study of the Influence of Duration. 

Our Commission gives no positive rule with regard to the effect of the duration 
of test, considering that the subject if not as yet sufficiently understood; it recom¬ 
mends, however, the continuance of study upon that subject. 

The Conventions declare for their part that the influence of time is incontestable, 
especially in tracing the diagrams in tensile tests, but they conclude that as yet they 
have not sufficient ground for establishing any fixed velocity of testing iron, copper, 
and bronze. 

On the other hand, in cold-bending tests they claim that the duration is of no 
importance. In operating upon heated materials they require that the tests shall be 
made as rapidly as possible, but this is doubtless in consideration of the cooling of 
the bar. 

The American Society requires that the duration of tests shall be noted. 

Chapter V.— General Observations upon Testing Apparatus. 

APPARATUS OPERATING BY GRADUAL ACTION. 

Machines for Tensile Tests. 

The Conventions confine themselves to demanding that machines properly handled 
shall not produce any shock on the test-pieces. They sanction the use of machines 
operated by hydraulic pressure or by a screw. They add that the test-pieces should 
be so mounted that the strain of tension or compression shall be uniformly distribu¬ 
ted throughout the cross-section. 

Besides those requirements, which coincide with those of our Commission, the 
Conventions include in their resolutions more explicit directions as to the mode of 
fastening the test-pieces for tensile tests than do we. 

For cylindrical test-pieces they propose the use of spherical bearings, preferably 
in one piece. 

They agree that test-pieces of rectangular cross-section shall be held at each 
extremity by a bolt passing through a slot provided for the purpose, or that the pieces 
shall be provided with milled heads and clamped by proper wedges. 

They forbid positively the use of the serrated wedges used by us, and that point 
should be submitted to a renewed examination by us. 


742 


APPENDIX. 


This last resolution is also adopted by the American Society, which, moreover,, 
recommends in positive terms the use of two special types of attaching apparatus in 
use in the United States. 

With regard to round test-pieces the American Society proposes to prolong the 
cylindrical section by conical bearings resting upon the clamping-pieces, in prefer¬ 
ence to threaded ends, such as are often used. This form is recommended for all 
metals except copper and its alloys, for which the Society considers it as yet impos¬ 
sible to give any standard type, conclusive experiments being lacking. 

Machines for Pressure Tests. 

The Conventions in their resolutions are in almost perfect accord with us on this 
subject. They require that the strain shall be carefully distributed throughout the 
cross-section, and point out that to attain such a result it is well so to place the pres¬ 
sure-plates that at least one may move easily and freely in all directions. 

Those resolutions recommend, moreover, the use of very smooth test-pieces; in 
other words, those which have been planed or turned; but this recommendation has 
reference only to the bearing-surfaces, since in speaking of castings they require 
besides that the faces of test-pieces for flexure and compression shall be left in the 
rough state. 

The American Society requires that the pieces to be tested shall be placed in 
position without the aid of any intervening medium whatsoever, such as wedges, 
supporting disks, etc., and that they shall be brought exactly into the axis of strain. 
That society repeats that the test-pieces should be prepared with the utmost care, 
the bearing-surfaces being exactly parallel and normal to the axis. 

Whenever tests are made upon large pieces horizontally placed it is necessary to 
take into account the initial flexure due to the weight of the piece as held in place. 

Machines for Transverse, Folding, Bending, and Curving Tests. 

The Conventions confine themselves to recommending slow-moving apparatus, 
acting either by pressure on the middle between two supports or by lateral pressure 
brought to bear upon one part of the test-piece, while the other is* securely held by 
clamping. Such apparatus should be simple and capable of being used rapidly. 
The weakest part of the test-piece should be clearly visible. 

For folding, they simply indicate that it should be done in a continuous manner, 
and that if a mandrel is used it should be of the smallest possible diameter, recom¬ 
mending in certain cases one with a fixed diameter of 25 millimeters. They repeat, 
moreover, that the angle of bending is not alone sufficient to indicate the deforma¬ 
tion, but that the radius of external curvature must be taken into account. 

The American Society recommends the use of a very simple apparatus for making 
bending tests upon mandrels of varying diameter, and prescribes the use of the hand- 
vise for bending, which is accepted by us, however, with certain restrictions. 

For transverse tests that society advises that supporting wedges shall not be 
used, preferring rolls that shall be displaced in proportion to the deformation by 
flexure of the bars. 

The foreign resolutions do not point out the different modes of testing by bend¬ 
ing that are specially defined by our Commission, but the Conventions state that the 
permanent committee should seek to determine, in the comparative tests remaining 
to be executed, the best method of measuring deformations. 

Machines for Torsion Tests. 

According to our conclusions, those machines should be arranged in such a 
manner that the axis of the piece will not sustain any flexure. 

The resolutions of the Conventions give no data upon this subject, but the Ameri¬ 
can Society has given definite instructions tending to prevent the production of any 
disturbing strains, such as transversal flexure or longitudinal tension over and above 
torsion properly so called. To this end the collars which hold the test-pieces should 
be exactly concentiic with it, to avoid giving any but a tangential strain. 


UNIFORM METHODS OF TESTING METALS. 


743 


APPARATUS OPERATING BY ABRUPT ACTION. 


The resolutions of the Conventions are generally in harmony with ours in princi¬ 
ple, but they give much more explicit directions for the setting up of testing-ham¬ 
mers, especially in the case of heavy machines intended to test whole pieces. They 
have adopted for this purpose, as a standard type of hammer, one weighing 1000 
kilograms, permitting in certain exceptional cases the use of one weighing only 500 
kilograms, and they have decided that every hammer of the standard type shall be 
stamped and officially registered. They require that the studies relating to the ques¬ 
tion of shock tests shall continue, and they have charged the permanent committee 
with collecting all new propositions relating to the installation of machines for shock 
tests. 


They accept hammers as we make them, of cast iron or forged steel; they add 
that the striking-surface should be of forged steel, finished by dovetailing and made 
secure by wedges in such a manner that the vertical centre of gravity of the whole 
may not be disturbed. 

This vertical should coincide with the axis of the leads and should be indicated 
by marks upon the anvil or the anvil-block. The proper arrangement of the striking- 
surface should be verified by means of suitable reference-points. 

We require, moreover, that the mass and shape of the hammer shall be perfectly 
symmetrical with respect to the plane of the leads. 

Our directions, more especially with reference to tests upon test-pieces, regulate 
the form of the face of the small hammers used, and they indicate even the radius 
of curvature to be given that face, depending on the kind of metal to be tested. 
They also give the different weights for such hammers used under similar circum¬ 


stances. 

According to the resolutions of the Conventions, the guided length of the hammer 
should be at least double the clear width between the guides ; we claim, however, 
only that it should be greater than the width between the guides. 

The Conventions require that the weight of the anvil-block shall be at least ten 
times that of the hammer, and that the foundations shall be inelastic. We require 
that the anvil block shall constitute, either alone or embedded in solid masonry, a 
solid mass from fifteen to twenty times heavier than the hammer. 

In the working of the detaching apparatus the Conventions agree with us that 
there should be no wedging. The Conventions advise the placing of the point of 
suspension upon the same vertical as the centre of gravity of the hammer, and to 
insert between the detaching device and the hammer a short flexible piece—for ex¬ 
ample, a chain or cord. They point out as a style to be recommended the detaching 
device adopted in Russia, which, however, from the sketch given, does not seem to 
be provided with an intermediate chain or cord 

In regard to the friction on the leads, they recommend that those leads should 
be lubricated with plumbago. They reject all apparatus having a work due to fric¬ 
tion greater than 2 per cent of the usual work. They describe a process of measur¬ 
ing friction by inserting a spring-balance between the hammer and its lifting-rope. 
r nfey propose to deduce the effective weight of the hammer from the effect produced, 
with a given height of fall, on a centrally mounted standard cylinder made of copper, 
of dimensions yet to be determined. 

For the height of fall they advise that 6 meters shall not be exceeded, as the set- 
tin<r up of hammers of greater height cannot be done with as much security or ex¬ 
actitude. They recommend the use of a sliding scale for measuring the effective 
work, so that the zero of the graduation may be set at the top of the piece^ to be 
tested. That scale should be divided into metric half-tons. (See Fig. 300, p. 378.) 

All of the recommendations of the Conventions with regard to the setting up of 
machines for shock tests are agreed to by the American Society ; the weight of the 
hammer and the height of fall are determined by the measures m use m America. 
The weights adopted are, respectively, 1000, 1500, and 2500 pounds lor testing large 
pieces (equal to 453, 653, and 907 kilograms), and the height of fall is fixed at 20 
feet (equal to 6.09 meters), allowing, however, without doubt, the adoption of a less 
height of fall in special cases. (See standard adopted by the National Car-buildeis 


Assoc’n, p. 379.) 


744 


APPENDIX. 


Chapter VI.— Examination of the Forces to be Measured. 

Our resolutions recommend in effect that the strains and deformations produced 
in all tests by continuous action shall be measured ; these form of necessity two 
great classes—the one of elastic and the other of permanent deformation. 

Concerning the period of elastic deformation, three limits of elasticity are dis¬ 
tinguished and defined, viz., the theoretical, the proportional, and the apparent. 
Concerning the period of permanent deformation, our resolutions define the maxi¬ 
mum load supported, and the load of rupture, properly so called, giving the defor¬ 
mation corresponding to each of those two loads. 

Neither the resolutions of the Conventions nor those of the American Society 
give any instructions common to all tests made by gradual action; they restrict 
themselves entirely to tensile tests. 

The Conventions require that during the elastic period there shall be sought the 
yield-point and the limit of proportional elongation, appearing at the same time to 
admit that those two limits are blended, and during the period of permanent defor¬ 
mation the maximum resistance and the beginning of contraction as well as the 
load of actual rupture with the corresponding section. 

The American Society requires the determination of the same information, 
excepting only the beginning of contraction, insisting especially upon the impor¬ 
tance of the yield point, which measurement it claims should be made with the 
greatest precision. 

It defines that limit as being the load which produces a modification in the rate 
of elongation, which would seem to identify it with the proportional limit; but 
farther on, in an annexed illustration, it requires that the limit shall be determined 
by noting the point at which the elongation is suddenly augmented, which brings 
us back to the apparent limit. 

The recommendations of that society prescribe, moreover, the measurement of 
the elastic elongation with a view of determining thereby the modulus or coefficient 
of elasticity, and they point out, to this end, a special process consisting of measur¬ 
ing the elongations between certain limiting loads, determined in advance. 

They also observe the smallest section of the test-piece under the action of the 
elastic limit (yield-point), and, after the test, the section of rupture. 

In the calculation of the strain brought to bear upon the unit of section, their 
resolutions add that it is necessary always to consider the initial appearance of the 
test-piece, and not the constantly-changing appearance under the different loads 
that it supports up to the limit of rupture. 

This resolution conforms with that of our Commission. lowever, as in experi¬ 
ments made upon copper and brass, a comparison of the .oads developed in the 
course of the tests with the corresponding deformations has given rise to interesting 
conclusions ; our Commission has expressed the hope that analogous studies shall 
be made in regard to iron and steel. 

Chapters VII and VIII.— -Mechanical and Technical Terminology. 

Those two questions have been examined by our Commission only, but w 7 e have 
not been able to establish any fixed laws in regard to them. They have not been 
considered by either the Conventions or by the American Society. 

FOURTH PART. 

DETAILED STUDY OF THE DIFFERENT METHODS OF TESTING . 

FIRST CLASS-METHODS OF TESTING- BY GRADUAL ACTION. 

Our Commission states in a general way that those tests should be made in a 
manner as continuous and as regularly progressive as possible, and that recom¬ 
mendation is in accord with that adopted by the Conventions with regard to tensile 
tests. 

The American Society agrees to this also in a general way, but it provides for 
stopping the strain at certain intervals, whenever it is necessary to make observa- 


UNIFORM METHODS OF TESTING METALS. 


745 


tions of deformation, which is the case, for instance, in measuring the elastic limit 
and the elastic elongation. The Society requires in such cases that the developed 
strain shall never be diminished, but that it shall be maintained continuously in 
action. 


Chapter I.— Tensile Tests. 

MEASURE OF STRESS AND ELONGATION. 

Our resolutions define the precision to be sought in the definition and scientific 
observation of the first two elastic limits previously described ; they point out that 
for such purpose the elongations should be measured to the nearest thousandth of a 
millimeter. 

Such precision is unnecessary for the determination of the third limit, called the 
apparent limit, or the beginning of great deformation under a constant load. 

Regarding the observations made during the period of permanent deformation, 
our Commission recommends that the maximum load that can be borne shall be 
measured, saying that it does not appear to be necessary to measure the load of rup¬ 
ture, while, as has been shown heretofore, this measurement is required by the 
Conventions and by the American Society. 

In regard to measuring elongation, our Commission believes that for current 
practical tests on products of the same well-known make it is sufficient generally to 
measure the total elongation after rupture; but in more exact tests it would be use¬ 
ful to make some special experiments with a view to determining the relative value of 
the different parts which compose the total elongation (distributed elongation and 
elongation of contraction). 

The foreign resolutions do not consider this distinction. They recommend 
simply a method of measuring the total elongation suitable for reducing the results 
to uniformity by disregarding the influence that the position of the section of rupture 
beyond the middle third of the test-piece may have upon the observed elongation. 
This method amounts in principle to doubling the measured elongation for a distance 
equal to one half the length of the test-piece, counting from the section of rupture 
on the side, where it is possible to measure it, in such a manner as to render the 
same conditions as would have obtained had the rupture occurred in the middle of 
the test-piece and had the elongation been produced freely on both sides. The result 
is to increase a little the effective elongation measured directly on the real test-piece. 

This method is inconvenient in that it is necessary in advance to divide the use¬ 
ful or test length into very small sections. The length of each section is fixed at 1 
centimeter in Germany and at a half or even a quarter of an inch in America (12 or 
6 millimeters). As the elongations during the course of the test are produced in a 
comparatively irregular manner upon the length of the test-piece, we may consider 
that they are not necessarily uniform at the ruptured section even when that is in 
the middle of the piece, and the method can give in this respect only approximate 
results. 

It is true that if recourse to that method is not desired it will be found necessary, 
according to our resolutions, to discard every test-bar whose elongation of contrac¬ 
tion is not integrally included between the reference-points; the resolutions of the 
Conventions, particularizing still further, give this same injunction when the section 
of rupture falls beyond the middle third of the gauged length. 

In regard to tensile diagrams, our resolutions declare that it does not seem 
necessary to have recourse to them, at least in current practical tests with a view to 
ascertaining the quality of the metal tested from a determination of the useful sur¬ 
face they present. 

The resolutions of the Conventions provide, however, for the use of diagrams, 
and require that their area shall be calculated up to the limit corresponding to 
rupture. They observe on this subject that without doubt, in principle, the work 
on the test-piece should be considered only up to the beginning of contraction, but 
that in most cases the work corresponding to that last period is of little importance, 
and the error thus produced cannot be very considerable. In cases where the 
diagram is not made by special apparatus, they advise making as many observations 
as possible during the test in order to trace tin; diagram by separate points. 


746 


APPENDIX. 


The resolutions of the American Society also provide for the use of such 
diagrams. 

With regard to the varying coefficients thus far proposed, our Commission finds 
it impossible to recommend them, and, moreover, the foreign resolutions make no 
mention of them. 

In regard to the precision to be sought in measuring strains and elongations, our 
Commission declares that for strains less than 5000 kilograms a determination to 
within 25 kilograms is sufficient, going up to the limit of 50 kilograms, when the 
strain exceeds 5 tons ; or, for the first class, to within one two-hundredth, and for 
the second to within less than one one-hundredth of the total sum. 

The Conventions state that on their part they will accept an error of one tenth 
of a kilogram per square millimeter for tensile strains corresponding to the elastic 
limit (yield-point) and to that of rupture, which leads in practice, especially for the 
load of rupture, to a much smaller proportion of error than we have permitted. 

The American Society makes no recommendation upon this subject. 

In measuring the dimensions of test-pieces and elongations our Commission rec¬ 
ommends a determination to within five one-hundredths of a millimeter in the case 
of dimensions equal to or less than 10 millimeters, and it accepts an approximation 
to within one tenth only when the length to be measured is greater than 10 milli¬ 
meters ; the limit is, therefore, to within more than five one-thousandths in the first 
case, and to within less than one one-hundredth in the second. 

The resolutions of the Conventions recommend a degree of precision reaching one 
one-thousandth in measuring the elongation of rupture, and of one one-hundredth 
in measuring the contraction of area (considered, no doubt, as being the section of 
rupture itself). 

They recognize, however, that in many cases these decimals are uncertain, and 
that it is not necessary to add others. They state that it is sufficient to take the 
dimensions of test-pieces to within one-tenth of a millimeter, which, considering 
the measurement of the thickness and the width of the section, gives a degree of 
precision inferior to that recommended by our Commission. 

They require that the elongation shall be measured on two diametrically opposed 
sides of the test-bar, in order that the mean may be taken of the sum of the lengths 
obtained by measuring upon each part respectively the distance comprised between 
the corresponding reference-point and the section of rupture. 

For rectangular test-pieces it is even proposed to make three measurements of 
elongation, taking them upon the two sides and upon one of the faces. The mean of 
the first, two measures should be given and the last one should be stated separately. 

The General Report of our Commission only mentions the use of elasticimeters, 
which are considered almost indispensable in determining the elastic limit (yield- 
point), but which seem less necessary for the simple measurement of the total 
elongation. 

With the aim of measuring the section of rupture with all possible precision our 
resolutions propose that the measurement of the dimensions shall always be made at 
two opposite points, and that there shall be considered either the circle of mean 
diameter, or the rectangle of mean dimensions, according as the test-pieces have 
circular or rectangular sections. 

DIMENSIONS OF TEST-PIECES. 

In order that the proximity of the heads shall not interfere with the observed 
results, especially in the measurement of elongation, our resolutions require that 
the distance from the springing or end of the heads to the reference-points must be 
equal at least to the diameter or to the greater side of the transverse section of the 
test-piece; they consider that under such conditions the form of the heads is not 
important. 

The Conventions limit themselves to remarking that for cylindrical test-pieces the 
actual length of the cylindrical part should exceed the test length by at least 10 
millimeters,* which may be interpreted, doubtless, as imposing a uniform minimum 


* The original resolutions require that the actual length shall exceed the test length bv 20 milli¬ 
meters.—O. M. C. 




UNIFORM METHODS OF TESTING METALS. 


747 


of 5 millimeters of waste length at each end, regardless of the diameter of the test- 
piece, which may be 10, 15, 20, or 25 millimeters. 

The American Society gives regulations analogous to those of the French Com¬ 
mission. It lequiies that with round test-pieces the distances reserved beyond each 
reference-point shall be equal to or greater than a diameter. For flat or built-up 
square test-pieces its regulations require once and a half the width of the section or 
the side of the square. 

In order to make a comparison of the total elongations, taken after the rupture 
of circular test-pieces of different design, our Commission has decided to establish a 
fixed relation between the transverse section and the useful or test length of the 
test-piece. This relation, deduced by the law of similarity, shows that the test 
length should be proportional to the square root of the cross-section, and that fun¬ 
damental law has been admitted also by the Conventions. The only difference is in 
respect to the value of the coefficient adopted. 

While our formula 


P = 66.67A, 
or l = 8.18 VA, 

resutls in giving a diameter of 27.64 millimeters to a test-piece, having a test length 
of 200 millimeters, the formula of the Conventions, 

l = 11.3 \/A, 

leads to a smaller diameter for the same test length, for it gives in fact a diameter 
of 20 millimeters to a test-piece 200 millimeters long. In a general way this formula 
recommends itself on account of its great simplicity, inasmuch as the calculation of 
the linear dimensions is immediate; the useful or test length amounting always to 
ten times the diameter. 

Our formula presents, on the other hand, the advantage of expressing the area 
by a simple number, for example, 600 square millimeters for a test-piece 200 milli¬ 
meters in length, considering that it is better to seek simplicity in expressing the 
cross-section—rather than in indicating the diameter, because, no matter what 
number expresses the diameter, the difficulty of measuring it is always the same, 
whereas it is only the section which intervenes in the calculations, and the adoption 
of a simpler number to express the section greatly facilitates such calculations. 

Notwithstanding the employment of the law of similarity, the two resolutions 
preserve well-defined normal types, to which they recommend that reference be made. 
These are four in number in the two cases. 

Our standards have, respectively, test lengths of 70, 100, 141, and 200 milli¬ 
meters ; cross-sections of 75, 150, 300, and 600 square millimeters, and diameters of 
9.77, 13.82, 19.55, and 27.64 millimeters. The standards of the Conventions give 
sections very closely resembling these, but their longitudinal dimensions are greater; 
they have lengths, respectively, of 100, 150, 200, and 250 millimeters for diameters 
of 10, 15, 20, and 25 millimeters. 

Those standard types are adopted for steel and iron, as well as for copper and its 
alloys; for castings, however, the Conventions prescribe test-pieces having a diam¬ 
eter of 25 millimeters, and a useful or test length of 200 millimeters. 

The American Society prescribes four standards with diameters, respectively, of 
0.4, 0.6, 0.8, and 1 inch, which equals 0.010, 0.015, 0.020, and 0.025 millimeter, but 
it preserves a constant useful or test length of 8 inches (0.2) meter, ignoring the 
differences which must occur in the measurement of total elongation by testing with 
a uniform length and a variable diameter. 

The test length of 8 inches, as well as the various diameters given, have been 
chosen, moreover, for the purpose of approaching as nearly as possible the measures 
of the metric system, counting 8 inches as equal to 200 millimeters. This is ex¬ 
pressly stated by the Society itself. 

The law of similarity thus admitted, as has been shown, for cylindrical test- 
pieces is extended by our Commission, with the same coefficient, to test-pieces of 


748 


APPENDIX. 


square cross-section, and even to pieces that are simply rectangular, observing care¬ 
fully certain restrictions established with a view to facilitate manufacture, by estab¬ 
lishing different series, in each one of which the width remains the same. 

The Conventions also extend the formula expressing the law of similarity to test- 
pieces of simply rectangular cross-section, but without introducing any definite 
restrictions. They recommend, however, that the section 30 by 10 shall be consid¬ 
ered as the standard, even when the breadth and thickness may be chosen at pleas¬ 
ure. 

When the thickness is given, as for plates, and when it does not exceed 24 milli¬ 
meters, a width of 30 millimeters should be adopted. 

Whenever the thickness exceeds 24 millimeters it should be considered as breadth, 
and a thickness of 10 millimeters should be given to the test-piece. 

When the testing-machines are not sufficiently powerful, the limit of 24 millimeters 
should be replaced by that of 1(3 or 17 millimeters. 

The American Society permits on its part a width of 1.2 inches (0.030 meter) for 
rectangular test-pieces having a thickness of less than 1 inch (0.025 meter). 

If the thickness reaches 1 inch, the measure of 0.8 inch (0.02 meter) will be taken 
for the width. 

In testing sheets and plates the crust produced in rolling should not be removed. 

In testing sheets there should be taken two samples having the total section of the 
bar. 

Besides the preceding rules just given, which are considered applicable only to 
rectangular test-pieces having a thickness of more than 5 millimeters, our Commis¬ 
sion has adopted special dimensions for test-pieces having a thickness of less than that 
figure, considering that it is not necessary to be guided by the law of similarity, be¬ 
cause that law is doubtless no longer applicable in such a case. 

The useful or test length of those thin test-pieces has been fixed uniformly at 100 
millimeters, without reference to the thickness or the nature of the metal to be tested. 

CONDUCT OF TESTS. 

Our resolutions recommend, as has been indicated, operating by progressive or 
gradual tension. This recommendation is also found in the resolutions of the Con¬ 
ventions, but the American Society permits interruption of the test, without reliev¬ 
ing, however, the action of the strain, for the purpose of making certain important 
observations during the course of the test, such as those relating to the elastic limit 
(yield-point). 

In general, the American Society recommends the utmost care in placing the test- 
pieces, so that they may be directly in the axis of the machine, and to this end it 
advises that it should be referred carefully to two normal planes intersecting each 
other in line with this axis. 

The Society also recommends placing test-pieces for tensile tests under a very 
slight initial strain (from 0.7 to 1.4 kilograms per square millimeter) before com¬ 
mencing observations, in order that the errors generally made at the beginning of a 
test may be avoided. 

In regard to the rate of testing, our Commission has confined itself to giving some 
approximate directions, and it observes, to that end, that the duration of a test, 
which should be in a certain measure a function of the volume of the test-piece^ 
should be comprised between one and six minutes for current tests on test-pieces of 
ordinary dimensions. This time may be reduced to thirty seconds for small test- 
pieces having a thickness of less than 5 millimeters. Care should be taken, espe¬ 
cially with soft metals, to avoid heating the bars. 

The foreign resolutions make no recommendations upon this subject. The Con¬ 
ventions, however, observe that in establishing the diagram of tensile test great 
importance should be attached to showing with what rapidity the diagram was 
traced. 


UNIFORM METHODS OF TESTING METALS. 


749 


Chapter II.— Pressure Tests. 

TESTS ON SHORT PIECES. 

For determining the elastic limit our Commission advises the employment of 
cylindrical test-pieces having a diameter of 27.65 millimeters (600 square millimeters 
in cross-section) and 100 millimeters of useful or test length; but for the determi¬ 
nation of the maximum resistance to compression or crushing the diameter of the 
standard test-pieces will be reduced to 19.56 millimeters (300 square millimeters of 
cross-section), and the useful length to 20 millimeters. 

The regulations of the Conventions propose in testing castings the use of cubes of 
25 millimeters a side, making them serve as samples for pressure-tests. In another 
passage, however, they recommend a height of 30 millimeters. 

They give no complementary information on the subject of that test, merely stat¬ 
ing that Wachler adopted 25 millimeters as the standard dimension in his studies. 

The American Society considers that pressure tests upon short test-pieces are of 
little interest, recommending, preferably, the adoption of pieces of a length of from 
10 to 20 diameters. 

However, when it is a question of determining the resistance to disaggregation, 
the use of cylinders 1 inch in diameter (0.025 meter) and 2 inches in height (0.050 
meter) is proposed. Whenever the elastic resistance is to be determined the height 
will be increased to 10 or 20 inches (0.254 meter or 0.508 meter), always keeping the 
useful or test length at 8 inches, as in tensile tests. 

TESTS ON LONG PIECES (FLAMBEMENT). 

Our Commission insists especially upon the interest of making buckling tests, 
stating that for iron and steel the resistance determined by the tests thus made is in 
no way proportional to that determined by tensile tests, and in the existing state of 
science cannot be deduced from the results obtained by the usual tests. 

The Commission declares that the tests can be made on riveted pieces or on bars 
cut up for this purpose, and it observes that to render the two tests comparable it is 
sufficient that the ratio of the length of the test-piece to the minimum radius of 
gyration of the section should have the same value. In tests upon test-pieces the 
Commission proposes to give to that ratio values which are multiples of 5 or 10. 

It recommends that those tests shall always be made under well-defined condi¬ 
tions, such as those by perfect hinging or complete clamping. The precautions to be 
observed in the first case are prescribed, but it is added that no satisfactory disposi¬ 
tion for such testing by clamping is yet known. 

The foreign resolutions give no particular instructions regarding pressure tests 
on long pieces. However, the American Society provides for tests upon pieces 
having a diameter of 1 inch and from 10 to 20 inches long for determining the elastic 
limit (yield-point). 

It requires that the process shall be the same as in tensile tests, dividing the 
useful or test length into small sections in such a manner that the loss in value 
sustained may be determined from its elements, and that the calculation of the 
modulus and the coefficient of elasticity shall be made under like conditions. 

Chapter III.—Transverse Tests. 

TESTS ON TEST-PIECES. 

Castings. 

Our Commission adopts for standard bars a section having a side of 40 milli¬ 
meters, indicating that the total length should be determined in such a manner as to 
give a useful or test length of 150 or 500 millimeters according to the apparatus used 
(Monge or Joessel balance) 

The Conventions have adopted a prism 3 centimeters on a side, with a total 
length of 110 centimeters, giving a useful or test length of 100 centimeters. They 


750 


APPENDIX. 


recommend measuring the resistance to flexure up to the point of rupture and the 
corresponding work on three test-pieces. The faces of the pieces should be left in 
their rough condition. 

Our Commission prescribes that the faces of the bars shall be shaped by a machine 
and the edges rounded by a file. It regulates finally the duration of the test, which 
should be comprised between one and two minutes. 

The American Society requires for scientific tests that the effect of superficial 
quenching shall be avoided by using bars measuring at least 2 inches on a side 
(0.050 meter) or 2^ inches in diameter (0.063 meter). In current practical tests 
there will be used bars measuring only 1 inch (0.025 meter) on a side, taking the 
necessary precaution to throw aside surfaces which have been hardened or marked 
with blow-holes. 

/Steel Plates for Springs. 

Our Commission fixes the length to be adopted for developed test bars at 1 meter, 
the section to be used, however, being preserved without any modification. 

The plate will be prepared under the same conditions as to quenching and 
annealing as the springs. 

For testing, it will be placed on two movable slides, the use of which is also rec¬ 
ommended by the American Society. 

The test will be continued without stopping or lessening the load and with a 
regular and continuous movement up to the limit fixed upon, in such manner that 
the duration of the whole test is comprised between two and five minutes. 

The foreign recommendations contain no special remarks upon that subject. 

The American Society recommends, however, in a general way, regarding trans¬ 
verse tests, that the sample should be placed firmly in a horizontal position to avoid 
supporting wedges, that the strain shall be brought to bear exactly in the middle and 
normal to the axis of the piece, and in a plane passing through the three strained 
points. It requires that the bars used shall be 1 inch (0.025 meter) on a side, have 
a length of 40 inches (1.016 meters), and that they shall be placed upon supports 36 
inches apart (0.914 meter). 

According to the resolutions of the Society, the deviations should be measured 
from a fixed and invariable base. It is well to determine them at points situated at 
stated intervals from the middle of the bar in such a manner as to obtain certain 
elements of the curve of flexure over the whole extent of the length, and especially 
in the vicinity of the elastic limit (yield-point). 

Certain values of the permanent deviation may also be determined. 

• 

TESTS ON FINISHED OR WHOLE PIECES. 

Springs of Parallel and Spiral Plates. 

Our Commission recommends in transverse tests that springs be subjected to a 
less strain than that which corresponds to permanent deformation. 

The American Society, on its part, proposes to apply the maximum working load 
and to determine the deviation produced by that test. The test load will be obtained 
by proceeding by pressure or by shock, according to circumstances, but it will be 
applied only once. 

Rails and Fish-plates. 

Our Commission recommends determining as nearly as possible the load cor¬ 
responding to the proportional limit of elasticity in testing those pieces; it adds that 
The duration of the tests should be comprised between two and five minutes. 

The foreign resolutions examine also the question of transverse tests by static 
pressure, requiring that they shall be considered from the two following points ot 
view : First, there will be determined the elastic limit (the point where the set be¬ 
comes permanent); second, there will be measured the flexibility under increasing 
loads, exceeding even the elastic limit. 

The American Society states that it is hardly practicable to subject either rails or 
axles to a transverse test by static pressure. 


UNIFORM METHODS OF TESTING METALS . 


751 


Chapter IV.—Folding, Bending, and Curving Tests. 

Our Commission proposes to adopt for those tests standard bars 40 millimeters 
"wide and 250 millimeters long, observing that the length may be reduced to 150 
millimeters for copper and its alloys. It recommends, besides, that those various 
tests shall be made by a machine so arranged ns to produce a slow progressive 
strain, and that in folding tests the initial fold shall be obtained with a radius of 
curvature differing as little as possible from that exacted for the limiting fold. 

For mechanical folding the use of the hydraulic press or hammer is recommended. 

Our Commission gives, besides, certain directions for folding done by a hand- 
wise. It is necessary to observe here that this mode of testing is prohibited by the 
American Society. 

In regard to bending tests, our Commission has not yet fixed upon any stated 
diameter for the mandrel. 

For curving tests it proposes to adopt such machines as will permit the measure¬ 
ment at each instant of the developed strain and the corresponding deformation. 

The Conventions recommend, as has been indicated, the use of slow-moving ap¬ 
paratus, acting either upon the middle or at the extremity of the test-bar, but they 
require especially bending around a mandrel for the hot and cold folding test of 
irons and steels of all kinds, fixing upon a diameter of 25 millimeters for mandrels 
to be adopted in the case of wrought or cast-iron for bridges and of boiler-plates 
more than 6 millimeters in thickness. The mandrel should not be removod during 
the test until the ends of the test-pieces have become parallel to each other, and the 
bending will be continued to the point of contact in the case of test-pieces of copper. 

They add that the test-pieces employed should have a rectangular section, the 
width of which should be three times the thickness, and that the edges should be 
slightly rounded. 

They observe, besides, that the angle of folding alone is not sufficient for judg¬ 
ing of the degree of deformation of the test-piece, but that it is also necessary to 
take into account the radius of external curvature. They propose to make this 
measurement direct by means of templets, or to deduce it from the measure of the 
elongation upon the exterior face. 

They require, finally, that the permanent committee shall search for the most 
convenient method of measuring deformations, and they also require that it shall 
look into folding tests made upon defective pieces. 

The American Society also recommends the bending test around a mandrel, but 
it prescribes the use of mandrels of variable diameters, and it recommends giving 
them a diameter equal to twice the thickness of the bar to be tested. 

It approves, finally, the use of a very simple apparatus which shall permit that 
test to be made rapidly. It fixes 1 inch (0.025 meter) as the standard width to be 
given test-pieces for folding tests. 

Chapter V.—Torsion Tests. 

Our Commission confines itself to expressing the hope that experiments shall be 
continued with regard to the study of torsion. 

The American Society has given certain instructions, previously indicated, with 
regard to the installation of apparatus to be used in those tests. 

"with regard to test-pieces, it recommends the use of cylindrical heads, prohibit¬ 
ing absolutely square-shaped heads. It gives a sketch of the position to be given 
the fastenings, and it demands that the distance between the head and the nearest 
point of reference shall not be less than one diameter. 

It gives nothing concerning the determination of the useful or test length. 

Chapter VI.—Mixed Tests (Shearing and Punching). 

Our Commission has expressed the wish that the study of those tests may be 
continued, and it has proposed certain recommendations which may serve as a 
beginning for subsequent regulation. 

The resolutions of the Conventions say nothing upon this subject; they recom- 


752 


APPENDIX. 


mend only that certain plates, like those of wrought iron for boilers, shall be sub¬ 
mitted to the punching test, but they claim that the test is useless for plates of mild 
steel or ingot iron, which should never be punched. 

The American Society remarks that in this test special care should be taken to 
determine the space to be reserved between the edge of the finished bar and the 
edge of the hole punched in the interior of the section, in order that cracks may not 
be formed. 

This question is being studied by numerous experts both in France and in America. 

SECOND CLASS.-METHODS OF TESTING BY ABRUPT ACTION. 

Our Commission, in common with the foreign resolutions, indicates the particu¬ 
lar interest to be found in shock tests, for they give information which gradual 
action cannot furnish. It recommends that study concerning tensile tests by shock 
and the use of explosives may be continued. 

Chapter I. —Transverse Tests by Shock. 

Our conclusions relate especially to tests on test-pieces, as has been shown above. 
They fix the dimensions to be given to test the bars, according to the nature of the 
metal tested, regulating under the same conditions the weight of the hammer, the 
form of the striking face, and that of the edges of the supports. 

They recommend, besides, a continuance of theoretical research, to ascertain the 
respective effects of the two elements which are the component parts of the energy 
of shock, namely, the weight of the hammer and the height of fall. They require 
that for each metal there shall be determined the height of fall above which the 
fragility increases rapidly, that there shall be studied the effect of constantly increas¬ 
ing heights of fall in ordinary transverse tests made on test-pieces resting upon two- 
supports, and finally that there shall be studied tests made by bringing the shock 
to bear upon the free end of test-pieces clamped at one end only. 

Those different subjects are not examined in the foreign resolutions, which give 
special attention to tests upon whole pieces, and determined, as has been indicated, 
the weight of the hammer and the height of fall to be used. 

In tests upon finished pieces the resolutions of the Conventions recommend the 
use of bearing blocks or caps of such form that the upper surface of the piece shall 
be perfectly horizontal, the face of the hammer being always perfectly smooth and 
plane. Those pieces should be as light as possible. 

Our Commission appears to think, however, that the use of those caps may be 
dispensed with when it is a question of testing pieces before sustaining in service 
blows which would be of such a character as to alter them. 

In a paper on shock tests, presented to the American Association for the 
Advancement of Science at its meeting of August, 1894, in Brooklyn, by Prof. Mans¬ 
field Merriman, vice-president of the society, the author recommends the disuse of 
those caps; he proposes to give the hammer a large striking surface to avoid loss 
of energy by heat, and to take account of the rebound of the hammer. 

The Conventions claim, on the other hand, that the data derived from tests thus 
far made are not sufficiently conclusive to admit of giving any fixed form for either 
the supports or the pieces destined to receive the shock. 

In observations on the results they declare that it is sufficient to determine the 
curvature deflection to within about i millimeter, when it is measured on a cord 
of from 1 to 1.5 meters in length. 

In a general way they recommend, as has our Commission, the taking of careful 
notes regarding all the peculiarities of the test, stating, for example, whether there 
had been any interruption during the test, whether the piece had been turned over, 
etc. 


Chapter II.— Superficial Penetration Tests by Shock. 

That mode of testing, minutely studied by our Commission, has not been 
examined in the foreign resolutions.. 


UNIFORM METHODS OF TESTING METALS. 


753 


Chapter III.—Perforation Tests by Shock. 

Our Commission has only been able to express a desire that new experiments 
should be made for the purpose of solving the various questions which have been 
brought up by that method of test. The study of that method of test has not, as 
yet, been broached by the Conventions or by the American Society. 


THIRD CLASS.-STUDY OF HARDNESS AND FRAGILITY. 

Chapter I.—Proposed Definitions and Methods of Measuring. 

Our Commission has reserved the study of that subject for a future session. 

Chapter II.—Tests of Hardness by Scratching and by ^Resistance to Wear 

• and Tear. 

Our Commission has expressed the hope that those two subjects might be the 
object of complemental studies. 

The Conventions have expressed a like hope in reference to the wear and tear of 
rails and tires, requiring that those tests shall be made under conditions as nearly 
like those of practice as possible. 

The American Society declares that it is impossible to present any recommend¬ 
ations upon that subject"; however, it points out that for rails it is proper to make 
tests upon curved pieces, and to take into consideration the action of shock, of 
rapid rolling, and of variations in temperature and humidity. 


Chapter III.—Folding Tests after Cold Hardening by Punching, or after 

Cutting. 

The Conventions have charged the permanent committee with searching for the 
causes of irregularities in ingot iron shown by unexpected breakages, notwithstanding 
tests upon the broken pieces had given satisfactory results. 

Our Commission considers that folding tests made after cold hardening ( ecrouis - 
sage) or cutting should show those irregularities, and it has given in this respect 
■certain practical rules which may in some measure bring out the information desired 
by the Conventions. 


FOURTH CLASS.—TESTS OF MANUFACTURE. 

Chapter I.—Cold-working Tests. 

The enlarging upon the mandrel, the heating, the flattening, and crushing tests, 
all studied in our resolutions, are not mentioned by the foreign resolutions. 

Chapter II.—Hot-working Tests of Irons and Steels. 

TESTS BY BENDING AND FOLDING. 

Our Commission points out certain tests to be made on plates, angle-iron, and 
facing-iron ; for bars cut from plates the same dimensions are assumed as for cold 

It points out that all these tests should be made at the same heat. 

The Conventions recommend that certain kinds of metals, such as ingot or 
wrought iron for bridges, and plates of ingot iron or mild steel for boilers, shall be 
subiected to the hot-folding test. For the latter a test will also be made after quench¬ 
ing The hot test is made around a mandrel under the same conditions as in cold 

bending. 


754 


APPENDIX. 


TESTS BY STAMPING, BENDING INTO HOOKS, BORING, PRESSING, FORGING, FLATTENING* 

AND WELDING. 

The greater part of those tests are not mentioned in the foreign resolutions, 
except those by flattening and welding. 

The Conventions recommend those two modes of test for different kinds of metals, 
without trying to establish any definite rules. 

They declare that it is difficult to generalize from tests by welding, since much 
depends upon the skilfulness of the operator, and they have determined to require 
a subcommittee to study the utility of the various hot tests. 

The American Society requires recourse to be had to the flattening test for testing 
riveted bars, and it states, as does our Commission, that the amount of spreading 
out obtained before the appearance of fissures furnishes one measure of the quality 
of the metal. 

It insists strongly on the welding test, stating that such a test has a special 
importance in the United States, inasmuch as welded pieces are frequently used 
there. • 

It gives the precautions to be observed in welding, which should be done at one 
temperature, a white heat, and it requires that after the operation the test-piece 
shall be submitted to a tensile test. 

Another sample should be submitted to a folding test after a groove has been 
made of a depth equal to that of the weld. 

The American Society demands that the welded bars shall be allowed to cool 
without being wet. 

It does not prescribe the boring or piercing test after welding recommended by 
our Commission. 

FIFTH CLASS.—SPECIAL TESTS ON CERTAIN FINISHED PIECES. 

The foreign resolutions insist strongly upon the great interest that there will be 
in being able to make tests upon the finished pieces themselves ; they require that 
in setting up testing-machines the possibility of making tests on finished pieces 
shall be kept in mind. They add that the shock test is generally the most important, 
and for certain pieces in frequent use on railroads they recommend or prescribe 
certain special tests. 

Our Commission', however, does not feel at liberty to formulate any such resolu¬ 
tions, and in making its studies of tests on finished pieces it confines itself to point¬ 
ing out the method of executing the tests without indicating that any one may be 
superior to the others. 


Chapter I.—Tests on Wire. 

Our Commission has studied the principal tests that may be made on wire, i.e. v 
tensile, folding, winding, and torsion. 

The Conventions require upon this subject only that the torsion test shall be 
made by means of suitable machines, and that the folding test shall be made by ma¬ 
chinery bending the piece alternately in two opposite directions around a mandrel 
5 millimeters in diameter. 

The American Society reproduces those conclusions, requiring, however, that the 
diameter of the mandrel shall be equal to that of the wire. 

The analogous test studied by our Commission is that of winding or wrapping. 
It requires that the diameter of the roller or spool shall vary according to the 
destined use of the thread, but requires that it shall be always a multiple of the. 
diameter of the wire. 

Chapter II.— Tests on Wire Rope. 

Our Commission prescribes the rules to be followed in tests for tension and flex¬ 
ibility. The Conventions and the American Society require that a tensile and a 
shock test shall be made in the longitudinal direction without giving any further 
details on that subject. Our Commission expresses the hope that the study of ten- 


UNIFORM METHODS OF TESTING METALS . 


755 


sile tests by shock may be continued, as well as the folding or winding tests, in order 
to furnish information as to flexibility. 

The Conventions add that the folding test is of value only when continued for a. 
given length of time. 


Chapter III.— Tests on Chains. 

Our Commission proposes submitting chains to a tensile test made at first under 
a moderate load, then carried to rupture, and it gives some instructions relating to 
the execution of that test. For the test under a moderate strain it proposes 
adopting a strain double that to be met with in actual service. 

The American Society requires only that the chain shall be subjected to the 
service strain, and that the elastic and permanent elongation shall be measured as 
well as the change in the form of the links. 

Chapter IV. —Tests on Rivets. 

As a special test on bars for rivets, the American Society presents only the hot 
flattening test. 

Our Commission gives two principal tests : one to separate the two riveted bands 
or bars by means of a chisel with a given bevel driven by blows of a hammer, and 
the other to subject those bars to a sort of shearing test. 

• » 

Chapter V.—Tests on Pipes and Tubes. 

The foreign resolutions give no special information in regard to the manufacture 
test to be made on pipes or tubes. 

Chapter YI.—Tests by Hydraulic Pressure. 

For tests of steam-boilers the American Society recommends the adoption of the 
method used by the Hartford Inspection Company, which is already in general use 
in the United States. 

Our Commission, without prescribing the methods of test required in France, 
points out the precautions to be observed and the verifications to be made in testing 
boilers. 

For testing cylinders and pipes the American Society proposes the application of 
a pressure equal to the maximum working load. It requires, besides, that the dila¬ 
tion of pipes under that load shall be observed, as well as the permanent dilation, if 
any be produced, and to mention whether the pipe leaks. 

In conclusion, our Commission recalls the fact that hydraulic pressure has been 
used recently to acquire desired data relating to the elastic deformation of metals 
and it expresses the hope that those studies may be extended to plates. 


APPENDIX D. 


SPECIFICATIONS FOR STRUCTURAL STEEL. 


I. PROPOSED BY A COMMITTEE OF THE AMERICAN SOCIETY OF 

CIVIL ENGINEERS, 1896. 

The following specifications for structural rolled and for cast steel are those 
recommended by the Committee of the American Society of Civil Engineers (1896): 

( Low steel. 60,000 lbs. ± 4,000 

Tensile strength-< Medium steel.. 65,000 “ ±4,000 

( High steel. 70,000 “ ±4,000 

Yield-point = 55$ of the ultimate resistance of specimen. 

1,500,000 


Per cent elongation in 8 in. = 


Ultimate* 


„ * , . 2,800,000 
Per cent reduction of area = Ultimate* 


Rivet-steel, when heated to a low cherry-red and quenched in water at 82° Fahr., 
must bend to close contact without sign of fracture. Specimens of low steel when 
treated and tested in the same manner must stand bending 180° to a curve whose inner 
radius is equal to the thickness of the specimen without sign of fracture. Specimens 
of medium steel, as cut from bars or plates and without quenching, must stand bend¬ 
ing 180° to an inner radius of one and one half times the thickness of the specimen 
without sign of fracture ; w T hile those of high steel, also without quenching, must stand 
bending 180° to a radius of twice the thickness of the specimen without sign of 
fracture. 

STEEL CASTINGS. 

In steel castings the tension test is recommended, with the following requirements: 

Ultimate. 65,000 lbs. per square inch. 

Yield-point. 35,000 “ “ 

Elongation in 8 in. = 15$ 

Contraction. =25$ 

The criterion for the elongation is that of Tetmajer, which consists in calling 
the product of the ultimate strength by the percentage of elongation the “coeffi¬ 
cient of quality.” The locus of this equation for the elongation, as given above, is 
shown in Fig. 74, p. 159, together with the ordinary limits of the elongation and a 
modified equation proposed by the author. 


II. SPECIFICATIONS PROPOSED BY H. H. CAMPBELL. 

(In liis work " The Manufacture of Structural Steel,” 1896.) 

General Provisions on Methods of Testing. —(1) Rivet-rods and other rounds 
are to be tested in the form in which they leave the rolls, without machining. 

Note .—This is apparently opposed to the recommendations of the Internalional 

756 









SPECIFICATIONS FOR STRUCTURAL STEEL. 


757 


Conferences,* wherein it is proposed that round test-pieces shall be turned to one of 
four standard diameters, with shoulders and screw-grip thread at each end, but it is 
stated elsewhere in the reports of the committee that only pieces for scientific inves¬ 
tigation are to be prepared in this manner. 

(2) Test-pieces from angles, plates, shapes, etc., shall be rectangular in shape, 
with a cross-sectional area of about one-half square inch, and shall be taken so that 
only two sides are machine-finished, the other two having the surface which was in 
contact with the rolls in the last pass. 

Note. —The report of the committee above mentioned recommends this method of 
cutting tests, but specifies that there shall be shoulders at each end. This necessi¬ 
tates considerable extra machine-work without any notable effect upon the result. 
The limitation of the area of the piece prevents the passing of inferior material by 
an unusual increase in width. 

(3) Should fracture occur outside of the middle third of the gauge length, the 
test is to be discarded as worthless if it falls below the standard. 

Note. —This provision is copied from the report of the above committee, and is 
much to be commended. A deficient elongation when the piece breaks near the 
end is not the fault of the material, but a mere accident. On eye-bars, a failure in 
the eye should condemn the method of forming the head rather than the quality of 
the steel. 

(4) In case one test-piece falls slightly below the requirements in any particular, 
the inspector shall allow the retesting of the lot or heat by taking four additional 
tests from the same lot or heat, and if the average of the five shall show that the 
steel is within the requirements, the metal shall be accepted. 

(5) Drillings for chemical analysis may be taken either from the preliminary 
test-piece or from the finished material ; but if the sample be taken from the centre 
of a sheared or universal-mill plate, the maximum limit of both phosphorus and 
sulphur shall be raised 25 per cent; e.g., from .04 to .05 per cent, or .08 to .10 per 
cent. 

(6) The pulling speed of the machine for breaking test-pieces shall not be less 
than one-quarter inch per minute nor more than three inches per minute. 

(7) The elastic limit shall be determined by the dropping of the beam. 

Classes of Steel Proposed.—The following specifications do not deal with metal 

for special purposes, like gun-carriages, armor-plate, etc., but are intended to cover 
more or less fully the needs of the structural engineer. I do not expect that they 
will ever be adopted in their entirety as standard requirements, but this seems to 
be the simplest form in which to condense the investigations that have been recorded 
in the foregoing chapters, and to present the variations in the physical properties 
caused by changes in the history and section of the test-piece. 

Engineers who do not wish to cumber their specifications with so many allow¬ 
ances for thickness and section will find herein the reason for many troublesome 
questions arising in the testing of the material, for I have tried to tabulate, as fairly 
as can be estimated, the effect of conditions that are ruled more by the laws of nature 
than by the skill of the manufacturer. 

At the same time it will be found that the matter is not as complicated as 
would be indicated at first sight, for one page of general provisions and one page of 
physical limits for each kind of steel can hardly be called a very voluminous docu¬ 
ment to cover the specifications upon structural shapes. 

The engineer who will compare the proposed requirements with what is demanded 
in other countries will find a remarkable difference. The specifications which are 
in general use in Germany are as follows!: 

For Rivets. —Ultimate strength from 51,200 to 59,700 pounds per square inch ; 
elongation 22 per cent in eight inches. 

For Other Structural Material. —Lengthwise tests : Ultimate strength from 
52,600 to 62,600 pounds per square inch ; elongation 20 per cent in eight inches. 

Crosswise tests : Ultimate strength from 51,200 to 64,000 pounds per square 
inch ; elongation 17 per cent in eight inches. 


* Report of Committee on Standard Tests to the Am . Soc . Mech . Eng .. Appendix V. 
t Noi-malbedingungen fiir die Lieferung von Eisenconstruktionen fur Brurken - und Hochbau 
(Otto Meissner, 1893); also, Ueber die Arbeiten der Flusseisen-Commission (F. Kintzl6, 1892). 





758 


APPENDIX. 


These are given as the limits accepted by the leading engineering societies of that 
country, and I am informed by Mr. Kintzle* that they represent the general re¬ 
quirements at the present time for all classes of material. It is safe to say that if 
American engineers were satisfied with the German standards, there would not be 
one rejection for deficient ductility where there are twenty under our more rigid 
requirements ; and if they would be content with a steel having an ultimate 
strength between 52,000 and 62,000 pounds per square inch, there would not be 
one fifth the number of heats discarded for being outside of the tensile limits. The 
bearing of these facts upon the cost of the material is self-evident. 

I do not advocate any sacrifice of strength to economy, but I would impress upon 
American engineers that this soft metal is eminently suitable for structural work, 
while by maintaining their present chemical limitations and their requirements con¬ 
cerning ductility they will be assured of a material which is equal in quality to any 
produced in the world. 

CLASS I.—EXTRA DEAD SOFT; FOR COMMON RIVETS, WIRE CABLES, AND OTHER 
PURPOSES WHERE EXCEPTIONAL TOUGHNESS IS REQUIRED. 


Method of manufacture: Basic open-hearth process. 

Chemical composition, in per cent: P below .04; S below .06; Si below .04; Mn below .50, 
Physical requirements as follows: 


Shape. 

Diameter in 
Inches. 

Ultimate 
Pounds per 

Minimum. 

Strength, 
Square Inch. 

Maximum. 

Elastic Ratio. 

Elongation 
in 8 Inches, 
Per Cent. 

Reduction 
of Area, 

Per Cent. 

Rivet-rods 

% 

46000 

55000 

64.0 

28.0 

52 

44 

% 

46000 

54000 

63.0 

29.0 

58 

ii 

Vs 

45000 

54000 

61.5 

29.25 

56 

4 4 

1 

45000 

54000 

60.0 

29.50 

54 

44 


44000 

54000 

58.5 

29.75 

52 

44 

m 

44000 

54000 

57.0 

30.00 

50 


A rolled round about three-quarters inch in diameter, after being nicked about 
one-quarter way through, shall bend completely double without fracture, with the 
nick on the outer curve of the bend. 

Heats rolled into bars less than five-eighths inch in diameter may be tested in 
trial rods of three-quarters inch. 

If any bar fails to pass the physical tests, four more pieces shall be taken from 
the same heat, and the average of all five bars shall be considered the true record. 

Pwivets, when cut out of the work into which they have been put, shall show a. 
tough silky structure, with no crystalline appearance. 

See also general provisions, p. 756. 

CLASS II.—BRIDGE RIVETS; FOR RIVETS IN RAILROAD BRIDGES. 

Method of manufacture: Acid or basic opeu-hearth process. 

Chemical composition, in per cent: P below .04 in acid steel, below .03 in basic; S below .05; Si 
below .04; Mn below .50. 

Physical requirements as follows: 


Shape. 

Diameter 
in Inches. 

Ultimate Strength, 
Lbs. per Square Inch. 

Elastic 

Ratio. 

Elongation in 8 Inches, 
Per Cent. 

Average 
Reduction 
of Area, 
Per Cent. 

Minimum. 

Maximum 

Average. 

Minimum. 

Rivet-rods. 

% 

48000 

57000 

66.0 

29.0 

27.0 

60 

it 

H 

48000 

56000 

65.0 

30.0 

28.0 

60 


Va 

47000 

56000 

63.5 

30.5 

28.5 

58 


1 

47000 

56000 

62.0 

31.0 

29.0 

56 


m 

46000 

56000 

60.5 

31.0 

29.0 

54 


m 

46000 

56000 

59 0 

31 0 

29.0 

52 


♦Private communication, February, 1896. 











































SPECIFICATIONS FOR STRUCTURAL STEEL. 


759 


Two tons of bars from the same heat shall constitute a lot, and two specimens, 
each from a different bar, shall be tested from each lot. The above table gives the- 
average required of these two bars, and the minimum below which no bar shall fall. 
If the average elongation or reduction of area on any one lot shall fall below the 
requirement, two additional bars shall be cut from the same lot, and the average 
of the four pieces shall be considered the average of the lot, provided that no con¬ 
cession be made in the minimum. Heats rolled into sizes less than five-eighths 
inch may be tested in trial rods of three-quarters inch. 

A rolled round about three-quarters inch in diameter, after being nicked one- 
quarter way through, shall bend completely double without fracture, with the nick 
on the outer curve of the bend. A piece of three-quarter-inch rod cut one-half inch 
long shall be upset while cold into a disk one-eighth inch thick, without developing 
extensive flaws or showing signs of cold-shortness. 

Rivets, when cut out of the work into which they have been put, shall show a 
tough silky structure, with no crystalline appearance. 

See also general provisions , p. 756. 

CLASS III.—HARD BRIDGE RIVETS; A SUBSTITUTE FOR CLASS II, GIVING 

GREATER STRENGTH WITH LESS TOUGHNESS. 

Method of manufacture: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .01 in acid steel, below .03 in basic; S below .05; Si 
below .04; Mn below .00. 

Physical requirements as follows: 


Shape. 

Diameter 
in Inches. 

Ultimate Strength. 
Lbs. per Squai'e Inch. 

Elastic 

Ratio. 

Elongation in 8 Inches, 
Per Cent. 

Average 
Reduction 
of Area, 
Per Cent. 

Minimum. 

Maximum. 

Average. 

Minimum. 

Rivet-rods. 

% 

54000 

63000 

61.0 

28.0 

26 0 

55 

44 

% 

54000 

62000 

60.0 

29.0 

27 5 

55 

(4 

% 

53000 

62000 

58.5 

29.5 

27.5 

53 

U 

1 

53000 

62000 

57.0 

30 0 

28.0 

51 

(4 


52000 

62000 

55.5 

30.0 

28.0 

49 

44 

m 

52000 

62000 

54.0 

30.0 

28.0 

47 


Two tons of bars from the same heat shall constitute a lot, and two specimens, 
each from a different bar, shall be tested from each lot. The above table gives the 
average required of these two bars, and the minimum below which no bar shall 
fall. If the average elongation or reduction of area on any one lot shall fall below 
the requirement, two additional bars shall be cut from the same lot, and the aver¬ 
age of the four pieces shall be considered the average of the lot, provided that no 
concession be made in the minimum. Heats rolled into sizes less than five-eighths 
inch may be tested in trial rods of three-quarters inch. 

Rivets, when cut out of the work into which they have been put, shall show a 
tough silky structure, with no crystalline appearance. 

See also general provisions p. 756. 
























760 


APPENDIX. 


CLASS IV—COMMON HARD RIVETS; FOR ROOF-TRUSSES AND OTHER 

STRUCTURES NOT EXPOSED TO SHOCK. 


Method of manufacture: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .06 in acid steel, below .04 in basic; S below .05; Si 
below .04; Mn below .60. 

Physical requirements as follows: 


Shape. 

Diameter in 
Inches. 

Ultimate Strength, 
Pounds per Square Inch. 

Elastic Ratio. 

Elongation 
in 8 Inches, 
Per Cent. 

Reduction 
of Area, 
Per Cent. 

Minimum. 

Maximum. 

Rivet-rods. 

% 

54000 

63000 

61 0 

27.0 

55 

4 l 

% 

54000 

62000 

60.0 

28.0 

55 

4 4 

% 

53000 

62000 

58.5 

28.5 

53 

44 

1 

53000 

62000 

57.0 

29.0 

51 

44 

m 

52000 

62000 

55.5 

29.0 

49 

44 


52000 

62000 

54.0 

29.0 

47 


Four tests shall be taken from each heat, and the average of these four shall 
conform to the above table. If the average elongation or reduction of area of any 
heat shall fall below the requirement, four additional bars may be cut from the 
same heat, and the average of the eight pieces shall be considered the average of the 
heat. Heats rolled into sizes less than five-eighths inch may be tested in trial rods 
of three-quarters inch. 

Rivets, when cut out of the work into which they have been put, shall show a 
tough silky structure, with no crystalline appearance. 

JSee also general provisions , p. 756. 


















SPECIFICATIONS FOR STRUCTURAL STEEL. 


761 


CLASS Y.—SOFT BRIDGE STEEL; FOR ANGLES, PLATES, BARS, ETC., FOR BRIDGES, 
CRANES, AND SIMILAR STRUCTURES EXPOSED TO SHOCK. 


Method of manufacture, in per cent: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .06 in acid steel, below .04 in basic; S below .07 in 
plates and angles, below .06 in eye-bars; Si below .04; Mn below .50. 

Physical requirements as follows: 


Shape. 

Thickness in Inches. 

Ultimate 
Strength, 
Lbs. per 
Sq.In. 

i 

Elastic Ratio. 

Elongation in 8 Inches, 
Per Cent. 

Reduction of Area, 

Per Cent. 

Remarks. 

s 

3 

a 

2 

i 

a 

3 

2 

3 

S 

Angles. 

% 

H 

% 

% 

% 

50000 

50000 

49000 

49000 

48000 

58000 

58000 

58000 

58000 

58000 

63.0 
61 5 
60.0 
58.5 
57.0 

29 0 
29.0 
29.0 
29.0 
29.0 

55 

53 

51 

49 

47 

One piece of %-inch angle must open out flat and another 
close shut without sign of fracture. 

Plates. 

5/16 

% 

% 

% 

1 

m 

53000 

51000 

50000 

49000 

48000 

47000 

63000 

61000 

60000 

59000 

58000 

58000 

65.0 
63.0 
62.0 
60 0 
58.0 
56.0 

23.0 

26.0 

26.0 

25.0 

24.0 

23.0 

44 

50 

50 

48 

46 

44 

On plates under 42 inches wide the required elongation 
shall be raised 1.5per cent, and the reduction of area 2.0 per 
cent. On plates over 70 inches wide the elongation shall be 
lowered 1.5 per cent, and the reduction of area 2.0 per cent, 
On tests cut crosswise from the sheet, the minimum tensile 
strength shall be lowered 3000 lbs., the elongation 3 percent, 
and the reduction of area 10 per cent. On universal mill- 
plates the allowance for transverse tests shall be 5000 lbs., 
5 per cent and 15 per cent. Both longitudinal and trans¬ 
verse strips cut from plates shall bend double flat. When 
every plate in the heat is tested, the minimum elongation 
and reduction shall be lowered 5 per cent. 

Eye-bars, 

annealed. 

H 

1 

2 

2y 2 

50000 

50000 

49000 

49000 

48000 

58000 

58000 

58000 

58000 

58000 

57.0 

56.0 

54.0 

53.0 

52.0 



The elongation in full length shall be 15 per cent in bars 
from 10 to 20 ft. long, 14 per cent in 21 to 25 ft., 13.5 per cent 
in 26 to 30 ft., and 13 per cent in 31 to 35 ft. 



. 

. 




Shapes.— In channels, beams, etc., the requirements on tests cut from the web shall be the same 
as for plates between 42 and 70 inches wide, with the same allowance for difference in thickness. In 
tests cut from the flange the minimum tensile strength shall be lowered 3000 lbs., the elongation 3 per 
cent, and the reduction of area 10 per cent. 


See also general provisions, p. 756. 


« 













































762 


APPENDIX. 


'CLASS VI.—MEDIUM BRIDGE STEEL; A SUBSTITUTE FOR CLASS V WHEN 
GREATER STRENGTH AND LESS TOUGHNESS ARE REQUIRED. 


Method of manufacture: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .06 in acid steel, below .04 in basic; S below .07 in 
plates and angles, below .06 in eye-bars; Si below .04; Mn below .60. 

Physical requirements as follows: 


Shape. 

Thickness in Inches. 

Ultimate 
Strength, 
Lbs. per 
Sq. In. 

Elastic Ratio. 

Elongation in 8 Inches, 
Per Cent. 

Reduction of Area, 
Per.Cent. 

Remarks. 

g 

zz 

s 

a 

s 

s 

s 

cd 

k-H 

s 

Angles. 

% 

H 

% 

H 

Vs 

5/16 

% 

14 

% 

l 

56000 
56< ‘00 
55000 
55000 
54000 

64000 

64000 

61000 

64000 

64000 

63.0 

61.5 
60.0 

58.5 
57.0 

27.0 

27.0 

27.0 

27.0 

27.0 

50 

48 

46 

44 

42 

One piece of angle, not over ^ inch thick, shall open out 
flat, and another close shut without sign of fracture. 

Plates. 

50000 

57000 

50000 

55000 

54000 

53000 

69000 

67000 

66000 

65000 

64000 

64000 

62.0 
60.0 
59.0 
57.0 
55 0 
53.0 

22.0 
25.0 
25.0 
24 0 
23.: 
22.0 

39 

45 

45 

43 

41 

39 

On plates under 42 inches wide the required elongation 
shall be raised 1.5 percent, and the reduction of area 2.0 per 
cent. On plates over 70 inches wide.the elongation shall be 
lowered 1.5 per cent, and the reduction of area 2.0 per cent. 
On tests cut crosswise from the sheet the minimum tensile 
strength shall be lowered 3000 lbs., the elongation 3 percent, 
and the reduciion of area 10 per cent. On universal mill- 
plates the allowance for transverse tests shall be 5000 lbs., 
5 per cent, and 15 per cent. Longitudinal strips shall bend 
double flat; transverse strips shall bend through 180 degrees 
around a pin 1 inch in diameter. When every plate in the 
heat is tested, the minimum elongatiou and reduction of 
area shall be lowered 5 per cent. 

Eye-bars, 

annealed. 

% 

i 

O 

56000 

56000 

55000 

55000 

54000 

64000 

64000 

64000 

64000 

64000 

56 0 
55.0 
53.0 
52.0 

51.0 

. 


The elongation in full length shall be 14 per cent in bars 
from 10 to 20 ft. long, 13 per cent in 21 to 25 ft., 12.5 per cent 
in 26 to 3C ft., and 12 per cent in 31 to 35 ft. 


Shapes.— In channels, beams, etc., the requirements on tests cut from the web shall be the same 
as for plates between 42 and 70 inches wide, with the same allowance in thickness. In tests cut from 
the flange, the minimum tensile strength shall be lowered 3000 lbs., the elongation 3 percent, and the 
reduction of area 10 per cent. 

Note.— The allowable content of phosphorus may be raised to .08 per cent for acid and .05 per 
cent for basic steel, if the best quality is not required, but other specifications must remain the 
the same. 


/See also general provisions, p. 756 








































SPECIFICATIONS FOR STRUCTURAL STEEL. 


763 


CLASS VII.—HARD BRIDGE STEEL. 

Method of manufacture: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .06 in acid steel, below .04 in basic; S below .07 in 
plates and angles, below .06 in eye-bars; Si below .05; Mn below .80. 

Physical requirements as follows: 


<D 

o. 

c3 

A 

W 


c /2 

JV 

Tio 

c 

< 


CO 

<v 

-4-> 

c3 


Ah 


CfT r~ 

a 
i i 

«S 


CO 

V 

A 


o 


.5 


CO 

CO 


<X> 

a 

o 


H 


^4 

% 


% 


u 

1 


% 

1 

W 

2 

2^4 


Ultimate 

Strength, 


Lbs. 

per 


Sq.In. 




6 


g 

’-3 

a 

c 

3 

Ph 


g 

3 

'3 

03 

C/2 

c3 

1 

3 

S 

60000 

68000 

62.0 

60000 

68000 

60.5 

50000 

68000 

50.0 

58000 

68000 

57.5 

57000 

68000 

56.0 

63000 

73000 

60.0 

61000 

71000 

58 0 

60000 

70000 

57.0 

50000 

60000 

55.0 

58000 

68000 

53.0 

57000 

68000 

51.0 

60000 

68000 

55.0 

60000 

68000 

54.0 

50000 

68000 

52.0 

50000 

68000 

51.0 

58000 

68000 

50.0 


cn 

a> 

.a 

o 

c 

HH 

qo 


e ti 
c a 

— j> 

h£ i. 

c u 
C Oh 

W 


a> 


< 4-1 

o 


a = 
.9 5 
o 

o 7_ 
3 v 
^Ph 

Oh 


26.0 

26.0 

26.0 

26.0 

26.0 


48 

46 

44 

42 

40 


20.0 
23.0 
23.0 
2.'.0 
21.0 
20.0 


34 

40 

40 

38 

36 

34 


Remarks. 


One piece of angle, less than y> inch thick, shall open out 
flat, and another piece close shut without sign of fracture. 


On plates under 42 inches wide the required elongation 
shall be raised 1.5 per cent, and the reduction of area 2.0 per 
cent. On plates over 70 inches wide, the elongation shall be 
lowered 1.5 per cent, and the reduction of area 2 0 per cent. 
On tests cut crosswise from the sheet the minimum tensile 
strength shall be lowered 3000 lbs., the elongation 3 per cent, 
and the reduction of area 10 per cent. On universal mill- 
plates the allowance for transverse tests shall be 5000 lbs., 
5 per cent and 15 per cent. Longitudinal strips shall bend 
double flat. Transverse strips shall bend through 180 degrees 
around a pin 1 inch in diameter. When every plate in 
the heat is to be tested, the minimum elongation and reduc¬ 
tion of area shall be lowered 5 per cent. 


The elongation in full length shall be 13 per cent in bars 
from 10 to 20 ft. long, 12.5 per cent in 21 to 25 ft., 12 per cent 
in 26 to 30 ft., and 11.5 per cent in 31 to 35 ft 


Shapes. —In channels, beams, etc., the requirements on tests cut from the web shall be the same 
as for plates between 42 and 70 inches wide, with the same allowance for difference in thickness. In 
tests cut from the flange the minimum tensile strength shall be lowered 3000 lbs., the elongation 3 per 
■cent, and the reduction of area 10 per cent. 

Note.— The allowable content of phosphorus may be raised to .08 per cent in acid and .05 per 
cent in basic steel, if the best quality is not required, but other specifications must lemain the 
same. 


See also general provisions, p. 756. 














































764 


APPENDIX. 


CLASS VIII.—EXTRA HARD BRIDGE STEEL; FOR SPECIAL STRUCTURES WHERE 

GREAT STIFFNESS IS ESSENTIAL. 

Method of manufacture: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .06 in acid steel, below .04 in basic; S below .07 in 
plates and angles, below .06 in eye-bars; Si below .10; Mn below .80. 

Physical requirements as follows: 


Shape. 

Thickness in Inches. 

Ultimate 
Strength, 
Lbs. per 
Sq.In. 

Elastic Ratio. 

Elongation in 8 Inches, 
Per Cent 

Reduction of Area, 

Per Cent. 

Minimum. 

Maximum. 


% 

64000 

72000 

61.0 

25 0 

45 

W 

0> 


64000 

72000 

59.5 

25.0 

43 


% 

63000 

72000 

58.0 

25.0 

41 

c 

H 

62000 

72000 

56.5 

25.0 

39 

<3 

% 

61000 

72000 

55.0 

25.0 

37 


5/1 6 

67000 

77000 

59.0 

18.0 

32 

03 

% 

65000 

75000 

57.0 

21.0 

38 

<D 

H 

64000 

74000 

56.0 

21.0 

38 

c3 

% 

63000 

73000 

54 0 

20.0 

36 

Ph 

l 

62000 

72000 

52.0 

19 0 

34 


m 

61000 

72000 

50.0 

18.0 

32 



64000 

72000 

54.0 



-A 

74 

1 

64000 

72000 

53 0 



S-3 

4U 

63000 

72000 

51.0 



• D 

£ C 

x 

2 

63000 

72000 

50.0 



^ G 

W cs 

2*6 

62000 

72000 

49.0 




Remarks. 


One piece of angle, about %-inch thick, shall open out 
flat, and another piece close shut without sign of fracture. 


On plates under 42 inches wide the required elongation 
shall be raised 1.5per cent, and the reduction of area 2.0 per 
cent. On plates over 70 inches wide the elongation shall be 
lowered 1.5 per cent, and the reduction of area 2.0 per cent. 
On tests cut crosswise from the sheet the minimum tensile 
strength shall be lowered 6000 lbs., the elongation 3 per cent, 
and the reduction of area 10 percent. On universal mill- 
plates the allowance for transverse tests shall be 5000 lbs , 
5 per cent and 15 per cent. Longitudinal strips shall bend 
double flat. When every plate in the heat is to be tested, 
the minimum elongation and reduction of area shall be 
lowered 5 per cent. 


The elongation in full length shall be 12.5 percent in bars 
from 10 to 20 ft. long, 12.0 per cent in 21 to 25 ft., 11.5 per 
cent in 26 to 30 ft., and 11.0 per cent in 31 to 35 ft. 


Shapes.— In channels, beams, etc., the requirements on tests cut from the web shall be the same 
as for plates between 42 and 70 inches wide, with the same allowances for difference in thickness. In 
tests cut from the flange the minimum tensile strength shall be lowered 3000 lbs., the elongation 3 per 
cent, and the reduction of area 10 per cent. 

Note.—T he allowable content of phosphorus may be raised to .08 per cent for acid steel and 
.05 per cent for basic, if the best quality is not required, but other specifications must remain the 
same. 


/See also general provisions, p. 756. 









































SPECIFICATIONS FOR STRUCTURAL STEEL. 


7 G5 


CLASS IX.—FORGING STEEL; FOR PINS AND MISCELLANEOUS FORGINGS AND 

FOR SPECIAL PLATES AND ANGLES. 


Method of manufacture: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .06 in acid steel, below .04 in basic; S below .07 in 
plates and angles, below .06 in eye-bars; Si below .10; Mn below .90. 

Physical requirements as follows: 


Shape. 

Thickness in Inches. 

Ultimate 
Strength, 
Lbs. per 
Sq. In. 

Elastic Ratio. 

1 

Elongation in 8 Inches, 
Per Cent. 

Reduction of Area, 

Per Cent. 

Minimum. 

Maximum. 


% 

70000 

POOOO 

58.0 

22.0 

42 

03 


70000 

80000 

56.5 

22.0 

40 

Tc 

% 

69000 

80000 

55.0 

22.0 

38 

a 

H 

68000 

80000 

53.5 

22.0 

36 


Vs 

67000 

80000 

52.0 

22.0 

34 


5/16 

73000 

83000 

56.0 

16.0 

30 


% 

71000 

81000 

54.0 

19.0 

36 


y 2 

70000 

80000 

53 0 

19.0 

36 


V 4 

69000 

79000 

51.0 

18.0 

34 

Ph 

i 

68000 

78000 

49.0 

17.0 

32 



67000 

78000 

47.0 

16.0 

30 


Remarks. 


One piece of angle %-inch thick, shall open out flat, and 
another piece close shut without sign of fracture. 


On plates under 42 inches wide the required elongation 
shall be raised 1.5 percent, and the reduction of area 2.0 per 
cent. On plates over 70 inches wide, the elongation shall be 
lowered 1.5 per cent, and the reduction of area 2.0 per cent. 
Longitudinal strips under y inch thick shall bend double 
flat. When every plate in the heat is to be tested, the 
minimum elongation and reduction of area shall be low¬ 
ered 5 per cent. 


When this steel is used for pins or forgings, a charge may be tested by rolling a 
small test ingot or piece of bloom into a bar with a cross-section of about 0.5 or 1.0 
square inch. This bar should have an ultimate strength of between 70,000 and 
80,000 pounds per square inch, an elastic ratio of 58 per cent, and an elongation of 
15 per cent in eight inches. This method will usually suffice to show the quality of 
the steel. If it is desirable to test the forged work, a bar should be cut from a rolled 
or hammered piece about six inches in smallest dimension, and turned to a three- 
quarter-inch round, two inches between shoulders. This should have an ultimate 
strength of between 67,000 and 80,000 pounds per square inch, an elastic ratio of 50 
per cent, and elongation of 20 per cent in two inches. The test-piece should be 
cut at a depth of about two inches from the outside. 

See also general provisions, p. 756. 
































766 


APPENDIX. 


CLASS X.—HARD FORGING STEEL; FOR MISCELLANEOUS FORGINGS. 
Method of manufacture: Acid or basic open-hearth process. 

Chemical composition, in per cent: P below .05 in acid steel, below .03 in basic; S below .07; S 
below .10; Mn below .90. 

Physical requirements as follows: 



Ultimate 
Strength, 
Pounds per 
Square Inch. 

6 

Per Cent. 

1 

Shape and Origin of Test-piece. 

Minimum. 

Maximum. 

Elastic Rati 

Elongation, 

A rolled bar with a cross-section of about 0.5 to 1.0 square inch, made 
from a bloom or test ingot. Elongation measured in 8 inches. 

75000 

100000 

55 

12 

A 94-inch round, 2 inches long between shoulders, cut from a rolled or 
forged piece about 6 inches in smallest dimension. Elongation meas¬ 
ured in 2 inches.. 

75000 

100000 

45 

15 



The first method will suffice for ordinary work to show the quality of the 
material. The second involves considerable expense and delay in cutting and finish¬ 
ing the piece, and there is necessarily much variation caused by the different sizes 
and shapes of forgings. The test-piece should be cut at a depth of about two inches 
from the outside. 

See also general pj'ovisions, p. 756. 


Classes XI, XII, and XIII.—For buildings, highway bridges, and other struc¬ 
tures not exposed to shock. 

The requirements on material for ordinary structures need not be so carefully 
drawn as in the case of railroad bridges. Hence it will suffice to accept the standard 
specifications of the Association of American Steel Manufacturers given on the 
following pages. They are here given in full, since the clauses relating to the 
inspection of material, and the allowance for overweights, apply equally to all 
classes of material. The Association did not limit the use of this metal to buildings 
not exposed to shock, for the matter of chemical composition was left open to the 
engineer, but, in common with almost all manufacturers, I must unqualifiedly con¬ 
demn the use of metal for a railway bridge that contains over .08 per cent of 
phosphorus, while I believe that .06 per cent should be the upper limit. 

















SPECIFICATIONS FOR STRUCTURAL STEEL. 


767 


III.—STANDARD SPECIFICATIONS GOVERNING THE CHEMICAL AND 
PHYSICAL PROPERTIES OF STRUCTURAL AND SPECIAL OPEN- 
HEARTH PLATE AND RIVET STEEL, AS ADOPTED BY THE ASSOCIA¬ 
TION OF AMERICAN STEEL MANUFACTURERS* ON AUGUST 9th, 
1895, REVISED JULY 17th, 1896, 

AND SINCE FORMALLY APPROVED BY THE FOLLOWING COMPANIES : THE BETHLEHEM 
IRON CO.; CAMBRIA IRON CO.; CARBON STEEL CO. ; THE CARNEGIE STEEL CO., LIMITED; 
CATASAUQUA MANUFACTURING CO.; CENTRAL IRON WORKS; CLEVELAND ROLLING MILL 
CO.; COLORADO FUEL AND IRON CO.; GLASGOW IRON CO.; ILLINOIS STEEL CO.; JONES & 
LAUGHLINS, LIMITED; LUKENS IRON AND STEEL CO.; OTIS STEEL CO., LIMITED; PACIFIC 
ROLLING MILL CO.; PASSAIC ROLLING MILL CO.; PAXTON ROLLING MILLS; PENNSYLVANIA 
STEEL CO.; POTTSTOW T N IRON CO.; POTTSVILLE IRON AND STEEL CO.; READING ROLLING 
MILL CO.; SHOENBERGER STEEL CO.; SPANG STEEL AND IRON CO.; WORTH BROS. 

STRUCTURAL STEEL. 

Process of 1. Steel may be made by either the Open-hearth or Bessemer 
Manufacture, process. 

Testing. 2. All tests and inspections shall be made at place of manufacture 

prior to shipment. 

Test-pieces. 3. The tensile strength, limit of elasticity, and ductility shall be 
determined from a standard test-piece cut from the finished material. 
The standard shape of the test-piece for sheared plates shall be as 
shown by the following sketch: 


«-About- 3 %j 


Jf- 




*Qr. 


r 


Parallel Section 
Not less than g’ 


-* 


PA 


TV 

* 


,/jyN l"N 

..About-iS-'- 


Piece to be of same thickness as the plate 


-|- jr 

l 

l 

Abo.ht 2 * 

i, 

I 

i 

I 

* 


On tests cut from other material the test-piece may be either the 
same as for plates, or it may be planed or turned parallel throughout 
its entire length. The elongation shall be measured on an original 
length of 8 inches, except when the thickness of the finished material 
5/16 inch or less, in which case the elongation shall be measured in a 
length equal to sixteen times the thickness; and except in rounds of 5/8 
inch or less in diameter, in which case the elongation shall be measured 
in a length equal to eight times the diameter of section tested. Two 
test-pieces shall be taken from each melt or blow of finished material, 
one for tension and one for bending. 

Annealed 4 Material which is to be used without annealing or further treat- 
Test-pieces ment is to be tested in the condition in which it comes from the rolls. 

When material is to be annealed or otherwise treated before use, the 
specimen representing such material is to be similarly tieated befoie 

testing. 


* These specifications, as amended from year to year by the manufacturers themselves, are likely 
to comein toverygeneral use, since any deviation from them will involve additional expense.-J. B. J. 

















768 


APPENDIX. 


Marking. 


Finish. 

Chemical 

Properties. 


Physical 
Properties. 
Rivet Steel. 


Soft Steel. 


Medium Steel. 


Pin Steel. 


Eye-bar Steel. 


Full-size Test 
of Steel 
Eye-bars. 


Variation in 
Weight. 


5. Every finished piece of steel shall be stamped with the blow or 
melt number, and steel for pins shall have the blow or melt number 
stamped on the ends. Rivet and lacing steel and small pieces for pin- 
plates and stiffeners maybe shipped in bundles securely wired together, 
with the blow or melt number on a metal tag attached. 

6. Finished bars must be free from injurious seams, flaws, or 
cracks, and have a workmanlike finish. 

7 ' Railway Bridges: [ Maximum Phosphorus .08 per cent. 


Steel for Buildings, 
Train Sheds, 

Highway Bridges, 
and similar structures: 


Maximum Phosphorus .10 per cent. 


8. Steel shall be of three grades, Rivet, Soft, and Medium. 

9. Ultimate strength, 48,000 to 58,000 pounds per square inch. 

Elastic limit, not less than one half the ultimate strength. 

Elongation, 26 per cent. 

Bending test, 180 degrees flat on itself, without fracture on 
outside of bent portion. 

10. Ultimate strength, 52,000 to 62,000 pounds per square inch. 

Elastic limit, not less than one half the ultimate strength. 

Elongation, 25 per cent. 

Bending test, 180 degrees flat on itself, without fracture on 
outside of bent portion. 

11. Ultimate strength, 60,000 to 70,000 pounds per square inch. 

Elastic limit, not less than one half the ultimate strength. 

Elongation, 22 per cent. 

Bending test, 180 degrees to a diameter equal to thickness of 
piece tested, without fracture on outside of bent portion. 

12. Pins made from either of the above-mentioned grades of steel 
shall, on specimen test-pieces cut at a depth of one inch from surface of 
finished material, fill the physical requirements of the grade of steel 
from which they are rolled, for ultimate strength, elastic limit, and 
bending, but the required elongation shall be decreased 5 per cent, 

13. Eye-bar material, 1£ inches and less in thickness, made of either 
of the above-mentioned grades of steel, shall, on test-pieces cut from 
finished material, fill the requirements of the grade of steel from which 
it is rolled. For thicknesses greater than 1| inches there will be allowed 
a reduction in the percentage of elongation of 1 per cent for each 1/8 
of an inch increase of thickness, to a minimum of 20 per cent for 
medium steel and 22 per cent for soft steel. 

14. Full-size test of steel eye-bars shall be required to show not less 
than 10 per cent elongation in the body of the bar, and tensile strength 
not more than 5000 pounds below the minimum tensile strength re¬ 
quired in specimen tests of the grade of steel from which they are 
rolled. The bars will be required to break in the body; but should a bar 
break in the head, but develop 10 per cent elongation and the ultimate 
strength specified, it shall not be cause for rejection, provided not more 
than one third of the total number of bars tested break in the head; 
otherwise the entire lot will be rejected. 

15. The variation in cross-section or weight of more than 2-J per cent 
from that specified will be sufficient cause for rejection except in the 
case of sheared plates, which will be covered by the following permissible 
variations : 

a. Plates 12^ lbs. or heavier, when ordered to weight, shall not 
average more variation than 2^ per cent, either above or below the 
theoretical weight. 

b. Plates from 10 to 12| lbs., when ordered to weight, shall not 
average a greater variation than the following: 



SPECIFICATIONS FOR STRUCTURAL STEEL. 


769 


I p to 75 inches wide, 2^ per cent either above or below the theoretical 
weight. 

75 inches and over, 5 per cent, either above or below the theoretical 
weight. 

c. For all plates ordered to gauge there will be permitted an average 
excess of weight over that corresponding to the dimensions on the order 
equal in amount to that specified in the following table : 


TABLE OF ALLOWANCES FOR OVERWEIGHT FOR RECTANGULAR 
PLATES WHEN ORDERED TO GAUGE. 

The weight of 1 cubic inch of rolled steel is assumed to be .2833 pound. 


Plates 1/4" and over in Thickness. 

Plates under 1/4" in 
Thickness. 

Thickness 
of Plate. 

Width of Plate. 

Thickness 
of Plate. 

Width of Plate. 

Up to 75 in. 

75 to 100 in. 

Over 100 in. 

Up to 50 in. 

50 in. and 
above. 

1/4 in. 
5/1G “ 
3/8 “ 
7/16 “ 
1/2 “ 
9/16 “ 
5/8 “ 
Over 5/8 “ 

10 percent. 
8 

7 

6 

5 

41 “ 

4 

3* 

14 per cent 
12 

10 

8 

7 

61 

6 

5 

18 percent. 
16 

13 

10 

9 

8$ 

8 

6J 

1/8 up to 5/32 
5/32 “ 3/16 

3/16 “ 1/4 

10 per cent. 
8* “ 

7 

15 per cent. 
12* 

10 



STRUCTURAL CAST IRON. 

1. Except where chilled iron is specified, all castings shall be tough 
gray iron, free from injurious cold-shuts or blow-holes, true to pattern, 
and of a workmanlike finish. Sample pieces, one inch square, cast 
from the same heat of metal in sand-moulds, shall be capable of sus¬ 
taining on a clear span of 4 feet 8 inches a central load of 500 pounds 
when tested in the rough bar 

SPECIAL OPEN-HEARTH PLATE AND RIVET STEEL. 

Testing and 1. All tests and inspections shall be made at place of manufacture 

Inspection, prior to shipment. 

Test-pieces. 2. The tensile strength, limit of elasticity, and ductility shall be 
determined from a standard test-piece cut from the finished material. 
The standard shape of the test-piece for sheared plates shall be as 
shown by the following sketch: 


-i-*- 

i 

Abo;ut a* 

i, 

I 

t 

i 

I 




^-About-3->; \ fc 


^ Parallel Section 


* 


Not less than g 




Mi 




TT 

♦ 

l 

- 


» fyJl*■ -T>k l%k-E t C.- - - 
H ..-.About- 


18- 


Piece to be of same thickness as the plate. 







































770 


APPENDIX . 


On tests cut from other material the test-piece may be either the 
same as for plates, or it may be planed or turned parallel throughout 
its entire length. The elongation shall be measured on an original 
length of 8 inches, except when the thickness of the finished material 
is 5/1G inch or less, in which case the elongation shall be measured in 
a length equal to sixteen times the thickness; and except in rounds of 
5/8 inch or less in diameter, in which case the elongation shall be 
measured in a length equal to eight times the diameter of section 
tested. Four test pieces shall be taken from each melt of finished 
material; two for tension and two for bending. 

Annealed 8 . Material which is to be used without annealing or further treat- 
Test-pieces. ment is to be tested in the condition in which it comes from the rolls. 

When material is to be annealed or otherwise treated before use, the 
specimen representing such material is to be similarly treated before 


Marking. 


Finish. 

Chemical 

Properties. 


Physical 
Properties. 
Extra Soft 
Steel. 


testing. 

4. Every finished piece of steel shall be stamped with the melt > 
number. Rivet steel may be shipped in bundles securely wired to¬ 
gether, with the melt number on a metal tag attached. 

5. All plates shall be free from surface defects and have a work¬ 
manlike finish. 


Extra Soft and 
Fire-box Steel: 


Maximum Phosphorus .04 per cent. 

“ Sulphur .04 k ‘ “ 

Flange or Boil- ( “ Phosphorus .06 “ “ 

er Steel : f “ Sulphur .04 “ “ 

Boiler-rivet [ “ Phosphorus .04 “ “ 

Steel : \ “ Sulphur .04 “ “ 

7. Steel shall be of four grades— Extra Soft, Fire-box, Flange or 
Boiler, and Boiler-rivet Steel. 

8. Ultimate strength, 45,000 to 55,000 pounds per square inch. 


Elastic limit, not less than one half the ultimate strength. 

Elongation, 28 per cent. 

Cold and Quench bends, 180 degrees flat on itself, without frac¬ 
ture on outside of bent portion. 

Fire-box Steel. 9. Ultimate strength, 52,000 to 62,000 pounds per square inch. 

Elastic limit, not less than one half the ultimate strength. 

Elongation, 26 per cent. 

Cold and Quench bends, 180 degrees flat on itself, without frac¬ 
ture on outside of bent portion. 

Flange or 10. Ultimate strength, 52,000 to 62,000 pounds per square inch. 

Boiler-steel. Elastic limit, not less than one half the ultimate strength. 

Elongation, 25 per cent. 

Cold and Quench bends, 180 degrees flat on itself, without frac¬ 
ture on outside of bent portion. 

Boiler-rivet 11. Steel for boiler-rivets shall be made of the extra soft quality 
Steel. specified in paragraph No. 8. 

Variation 12. For all plates ordered to gauge there will be permitted an 
when ordered average excess of weight over that corresponding to the dimensions on 

to Gauge, the order equal in amount to that specified in the following table, pro¬ 
vided no plate shall be rejected for liglP gauge measuring .01" or less, 
below the ordered thickness : 


771 


SPECIFICATIONS FOR STRUCTURAL STEEL 

TABLE OF ALLOWANCES FOR OVERWEIGHT FOR RECTANGULAR 
PLATES WHEN ORDERED TO GAUGE. 


The weight of 1 cubic inch of rolled steel is assumed to be .2833 lb. 


Plates and over in Thickness. 

Plates under in Thickness. 

Thickness of 
Plate. 

Width of Plate. 

Thickness 
of Plate. 

Width of Plate. 

Up to 

75 in. 

75 in. to 
100 iu. 

Over 

100 in. 

Up to 

50 in. 

5o in. and 
above. 

1/4 inch 
5/16 “ 
3/8 “ 
7/16 “ 
1/2 “ 
9/16 “ 
5/8 “ 
Over 5/8 “ 

10 per cent 

8 “ “ 

“ 44 

6 44 44 

5 44 44 

4£ 44 “ 

4 ‘4 14 

3i 44 44 

14 per cent 
12 “ “ 

10 “ “ 

8 “ “ 

44 14 

64“ “ 

6 “ “ 

5 “ “ 

18 per cent 
16 “ “ 

13 “ “ 

10 “ “ 

9 “ “ 

81 “ “ 

8 k4 44 

64 “ “ 

1 /8 up to 5/32 
5/32 “ 3/16 

3/16 “ 1/4 

10 percent 
84- “ “ 

J U 44 

15 per cent 
124 “ “ 

10 “ “ 



Variation 18. Plates 12| lbs. or heavier, when ordered to weight, shall not 
when ordered average more variation than 2} per cent, either above or below the 
to Weight, theoretical weight. 

Plates from 10 to 12| lbs., when ordered to weight, shall not 
average a greater variation than the following: 

Up to 75 inches wide, 2 \ per cent either above or below the theo- 
theoretical weight. 

75 inches and over, 5 per cent either above or below the theo¬ 
retical weight. 

































APPENDIX E. 

THE COMMERCIAL ANALYSIS OF PORTLAND CEMENT.* 

By Wm. B. Newberry. 

The remarkable growth of the Portland-cement industry within the past three or 
four years has had some unlooked-for effects in directions apart from the manufac¬ 
ture and sale of the product. In the United States especially the cement chemist 
has sprung up to solve the many questions regarding quality which both producers 
and consumers are so ready to propound. 

Specialization being the order of the day, it is but natural that from the general 
analyst should be evolved in time the cement expert who should devote his labors to 
this branch of the science alone, for there is so much to be done along this one line 
that the practical investigator must limit his field to narrow bounds if he wishes to 
thoroughly cover the ground. 

As yet, however, little has been done and less published along the more practical 
lines. Yicat, Le Chatelier, and others have gone deeply into the theoretical side of 
the question and have produced many interesting and valuable results. But the 
commercial analyst and technical cement chemist have been obliged to adapt general 
methods to particular uses and perhaps invent new schemes to suit their special work. 
This is well exemplified in the analysis of an ordinary cement, whether Portland or 
natural rock. The chemist is to-day frequently required to furnish in short time, 
with reasonable accuracy, analyses of cements covering the following constituents: 
silica, iron and alumina (usually together), lime, and magnesia. Sulphur is quite 
often required and carbonic acid occasionally. 

Turning to his authorities, Fresenius, Cairns, Furman, etc., our analyst finds 
many schemes for limestones, clays, feldspars, etc., all excellent of their kind and 
covering all possible ingredients down to the alkalies and manganese, but he will 
find nothing exactly suiting his requirements, for although some authors give 
methods for cement analysis (see Stillman’s Engineering Chemistry , p. 202) they are 
so complex, requiring considerable time, and going into unnecessary detail, that they 
are almost useless to the commercial chemist to whom time is an important factor. 

What is wanted, then, for practical work is a scheme covering the above-mentioned 
components and insuring correctness within two-tenths of one per cent. The pos¬ 
sible variation between two samples of the same cement is seldom less than two- 
tenths of one per cent for any ingredient, and for practical work greater accuracy 
is unnecessary except, perhaps, in rare cases where magnesia or sulphuric acid 
approaches a specified limit. It should be possible to carry through the analysis in a 
few hours, leaving only the magnesia to be weighed the following day, and possibly 
the sulphuric acid to be checked at the same time. 

The writer has used such a scheme with gradual modifications for the past four 
years and has found it eminently reliable for all purposes where extreme accuracy 
is not essential to the value of the results. No originality is claimed for this scheme, 
the separations being, without exception, those in frequent use among analysts, the 
only object of this note being to show how simply and rapidly a satisfactory analysis 
may be performed if extreme delicacy and the determination of unimportant elements 
are not required. 


* This paper was published in Cement and Engineering News for January 1898, and has been here 
introduced in the second edition of this work because of the extremely meagre information to be 
found on this subject in the standard treatises on chemistry and on cements. Mr. Wm. B. Newberry 
was joint author of the paper referred to in Art. 163, p. 187. 


772 





COMMERCIAL A A"A LYSIS OF FORT LAND CEMENT. 


i i >> 


In the first place it should be understood that Portland cement occupies a posi¬ 
tion b) itsell among substances to be analyzed and does not come under the general 
head of limestones, which are more or less completely dissolved in dilute acids, or 
the clays and feldspars, which, being refractory silicates and undecomposable by 
acids, lequiie to be fused with alkaline carbonates before undergoing decomposition. 

Portland cement will be found to dissolve more or less readily in dilute hydro- 
cliloric acid on digestion, but that solution is incomplete is shown bv the increased 
weight of the insoluble residue over that obtained by fusion with sodium carbonate, 
and the presence of small percentages of iron, alumina, lime, etc., in this insoluble 
residue when it is subjected to fusion. 

If, instead of dilute hydrochloric acid, we treat finely ground cement with more 
concentrated acid and to this add a few drops of nitric acid, very little besides the 
silica will remain undissolved on subsequent evaporation to dryness and taking up 
with water. 

Many chemists still adhere to the longer and undoubtedly more strictly accurate 
method of fusing the cement with sodium carbonate and digesting in hot water, but 
the results of both methods on the same sample have shown that digestion with 
concentrated acid is quite correct enough for the generality of analyses, provided 
the grinding of the sample has been sufficiently fine; in fact it is the method usually 
adopted in the laboratories of cement factories throughout the country. In detail it 
is as follows: 


Silica. 

Having weighed out one-half gram of the finely ground and dried cement it is 
transferred to a four-inch evaporating-dish and 10 c. c. of hydrochloric acid of 
about half strength (sp. gr. 1.20, diluted with its bulk of water) is added, together 
with a few drops of nitric acid, cone. The dish is covered with a watch-glass on a 
glass triangle and placed on the sand-bath, where it will gently boil itself down to 
dryness. It should remain until no odor of hydrochloric acid arises from it and is 
then removed and allowed to cool. 

A grave mistake is frequently made in not allowing sufficient time on the sand- 
bath for complete breaking down of the soluble silicates, which does not take place 
until all the hydrochloric acid is gone. It is well to err on the safe side; a little 
extra baking will do no harm if the heat is not too high. When cool 20 c. c. of the 
same half-strength acid used before is added and it is set again on the sand-bath, 
and boiled gently under a close cover. This is somewhat different from the books, but 
it is necessary to effect a complete solution of the soluble chlorides from the silica, 
and as the hydrochloric acid is useful later on it may as well be added now. After 
remaining at least ten minutes on the sand-bath 50 c. c. of water is added, the 
whole brought to a brisk boil and filtered, washing the silica with hot water until 
the acid is all gone. The filter-paper (ashless papers 11 cm. wide are used through¬ 
out) containing the moist silica is withdrawn from the funnel, placed in a weighed 
platinum crucible and ignited, and weighed in the customary way. 


Iron and Alumina. 

The filtrate from the silica is heated and ammonia added in slight excess. If 
this is carefully done so as to introduce only enough ammonia to render the solution 
slightly odorous, it need be boiled only a few minutes before filtering off the hydrox¬ 
ides of iron and aluminum. After rinsing the last of the precipitate from the 
beaker the funnel is taken from its support and the precipitate washed back into the 
original beaker with a jet of hot water without destroying the paper. The hydrox¬ 
ides are then redissolved in a little hydrochloric acid and reprecipitated with ammo¬ 
nia, boiled, filtered, washed with hot water, and then removed to a crucible, ignited, 

and weighed. . 

This second precipitation of iron and alumina is quite essential, since if it is 
neglected as much as three per cent of lime may be carried down with the hydrox¬ 
ides. 


774 


APPENDIX. 


Lime. 

The filtrate from the iron and alumina should measure about 300 c. c. It is well 
to use a No. 3 beaker holding 300 c. c. for the filtrate from the silica and to increase 
the size one number for each separation, ending with a No. 6 for magnesia. A few 
drops of ammonia should be added to it and it is then brought to boiling. At the 
same time 20 c. c. of a saturated solution of ammonium oxalate is heated to boiling 
in a small beaker and when both are in free ebullition the oxalate is added to the 
filtrate while the latter is briskly stirred. The whole is kept boiling a few minutes 
and is then set aside to cool. 

If the precipitation is conducted in this manner the lime will settle at once in 
large crystalline flakes, enabling the operator to filter as soon as sufficiently cool— 
best in about 20 minutes—wash with hot water and remove filter-paper with the 
precipitate, spreading the paper against the inside of the beaker in which the lime 
was thrown down. The precipitate is then washed into the beaker with a jet of hot 
water, and the paper finally rinsed with dilute sulphuric acid. 

Water to 300 c. c. and 6 to 10 c. c. strong sulphuric acid are now added, the 
whole brought to incipient boiling and titrated with a standardized solution of 
potassium permanganate, as described by Furman in his Practical Assaying, pp. 
216, 217. 

Magnesia. 

The magnesia is now determined by placing the beaker containing the filtrate 
from the calcium oxalate in cold water and, when thoroughly cooled, adding with 
stirring 20 c. c. of a saturated solution of ammonium phosphate. Allow the beaker 
to remain in the cold over night, filter, wash, ignite, and weigh the magnesium pyro¬ 
phosphate in the usual manner, without drying the filter-paper and precipitate, but 
using a low heat for the ignition until the magnesia is white. 

Sulphur. 

For the determination of the sulphuric acid three grams of the cement are 
digested as above with concentrated hydrochloric acid and a little nitric acid, run 
down to dryness, and the silica separated in the manner described, taking care, how¬ 
ever, that the hydrochloric acid used to take up the soluble portions after roasting 
is in but slight excess. Boil the filtrate from the silica and add 15 c. c. of boiling 
barium-chloride solution (saturated) and let stand. The barium sulphate may be 
filtered as soon as completely settled, which will be in perhaps an hour, but the 
writer has always found a perceptible deposit of barium sulphate in the filtrate if 
kept till next day. Experiments on the same sample have proved this remainder to 
be not more than three per cent of the total quantity of S0 3 —or, giving the actual 
results in an average case, S0 3 = 1.65$ and 1.70$, the first being filtered within an 
hour and the second the next day. 


Carbonic Acid. 

If it is required that the carbonic acid be determined, a very convenient method 
is found in Cairns’ directions for the analysis of limestone. The little apparatus 
therein described may be used for cements provided a little water is mixed with the 
sample in order that it shall not cake together when the acid is drawn into the flask. 
It may be said, however, that at the present day the better grades of Portland 
cement will show so little carbonic acid, unless they happen to be very old indeed, 
that two or three grams will be needed for its determination, and its presence is sel¬ 
dom inquired after. 

In the above process of analysis the writer is well aware that accuracy is some¬ 
what sacrificed to convenience and the saving of time, and, while sharing the general 
prejudice against abbreviated methods, still feels that there are many cases where 
extreme accuracy is of no greater value than close approximation. When it is con¬ 
sidered that two samples drawn from the same barrel of cement may, and very often 
do, vary as widely as one-half of one per cent, not only in the lime but in the minor 


COMMERCIAL ANALYSIS OF PORTLAND CEMENT. 


77& 


components as well, it is evident that an analysis which may be relied on as correct 
within two-tenths of one per cent comes well within the limits of variation between 
duplicate samples and is as good for practical purposes as a determination to four 
places of decimals. 

The principal point of recommendation for this scheme is this : A sample of 
cement can be completely analyzed, with the exception of magnesia, in four hours, 
and, allowing a small excess of time, four to six determinations can be carried along 
together. The percentage of lime may be read off directly from a table as soon as 
titrated, and if other elements are neglected the lime alone may be reported in an 
hour. 

The accuracy of the method for the elements existing in small quantities is 
shown by fifty comparative analyses made during the present year in which the 
same samples were analyzed by the above process in the writer's laboratory and 
simultaneously by one of the leading analytical laboratories in Philadelphia. The 
average difference for magnesia (MgO) was .078$ of the cement or 2.7$ of the total 
magnesia present, which ran about 2.85$ in the cement, while the sulphuric acid 
(S0 3 ) showed an average variation between the two methods of .071$ of the cement 
or 0.4$ of the total S0 3 present, which was constant at about 1.1$. This for an average 
of fifty samples, while far from a perfect result, shows that a fair idea of the com¬ 
position of a cement may be obtained with very little labor. 


APPENDIX F. 


PRESERVATION OF WOOD. 


By O. Ciianute, C.E.* 


With the opening of the railway era and the consequent great demand for 
timber renewed attention was turned to chemical methods for retarding the decay 
of wood, the more so as England, France, and Germany, which were so copiously 
wooded at the beginning of the Christian era, had been pretty well denuded by the 
year 1830. 

Many wood-preserving experiments had previously been tried, chiefly for the 
preservation of ships’ timbers, so that in a treatise on The Preservation of Tim¬ 
ber, by Wm. Chapman, C.E., published in London in 1817, the author gives, after 
noticing the writings of his predecessors, the records of their and his own experi¬ 
ments, made principally upon perishable woods or beef flesh, with the following 
substances : 


Corrosive sublimate. 
Sulphate of copper. 
Sulphate of zinc. 
Coal-tar oil. 
Sulphate of iron. 
Nitrate of silver. 


Carbonate of soda. 
Caustic soda. 
Arsenic. 

Common salt. 
Quicklime. 

Barytes. 


Copper and iron sul- 
Soap. [phates. 

Resin. 

Vegetable oils. 

Fish oils. 

Essential oils. 


Vapors of oils. 
Charring. 
Charcoal powder. 
Mineral coal. 

Ain mine. 
Selenite. 


It is thus seen that modern chemistry suggested, at an early day, almost all the 
substances likely to prove of value as antiseptics. In 1832 Kyan patented the use 
of corrosive sublimate, and his process became known as “Kyanizing.” In 1837 
Margary patented the use of sulphate of copper. In 1838 and 1*848 Bethel patented 
the application of coal-tar oil. or creosote, since known as “ creosoting,” and in 1838 
and 1840 Burnett took out patents for the application of chloride of zinc, which 
process was termed “ Burnettizing.” Many inventors followed with patents for all 
sorts of methods and substances, but the first-mentioned four antiseptics may be 
said to be the only ones which have proved of real value after these many years of 
experience, and of these only creosote and chloride of zinc are now extensively used. 

At the beginning wood preservation proved a tempting field for speculative 
experiments, and, as it takes from seven to ten years to ascertain the real value of 
any treatment, many processes, once well thought of, have proved failures in the 
end, so that, of late years, only few new proposals have been brought forward, and 
not many of these have proved to be of value. These have been chiefly modifica¬ 
tions in the mode of injection. 

The methods of application originally employed were the following: first, steep¬ 
ing the wood for several days in the chemical solution selected; second, vital suction 
of chemicals by the growing tree; third, forcing solutions through freshly cut logs 
by hydraulic pressure in the open air; and fourth, forcing solutions by hydraulic 
pressure applied in a closed vessel containing the wood. 

The first method is still employed in kyanizing; the second and third have been 
abandoned; and the fourth has been gradually modified and improved, until it is 
now almost universally used. In applying this the wood to be treated is first 
loaded upon small cars, and these are run into an iron cylindrical vessel, generally 


* Mr. O. Chanute, Past President Am. Soc. C.'E., has long been actively engaged in timber preserva¬ 
tion and in building preservation plants. He is the highest American authority on this subject. 

776 




PRESERVATION OF WOOD. 


777 


fiom 40 to 110 feet long 5 or 6 feet in diameter, and of appropriate strength. 
Then the door is hermetically closed and the vessel is filled with steam at a pressure 
Siiffidently low (fiom 18 to 20 pounds to the square inch) not to injure the strength 
of the timber. This steaming is intended to liquefy the sap and to warm up the 
wood especially the air contained in the sap-cells, and is continued from half an 
hour to three hours, in accordance with the condition of the wood or the subsequent 
treatment which it is to receive. Then the steam is let out and an air-pump is set 
at work to produce a partial vacuum (about half an atmosphere) in the vessel The 
result ot this is that the heated air in the sap-cells expands and drives out a portion 
ot the sap, which latter is pumped out and run to waste. The wood being thus 
piepared to receive the solution, this is run in and hydraulic pressure applied by 
means of pumps. The effect of this is to force the chemicals into the sap-cells of 
the wood, chiefly, it is believed, through the ends, and to compress whatever air 
may remain therein, so as to cause greater absorption. The pressure varies, at 
diffeient woiks, fiom 60 to 150 pounds to the square inch, and is maintained for 
from one to four hours. In some processes, as will be explained further on, several 
successive solutions are used. When the wood has been sufficiently impregnated, 
the solution is dii\en back into its storage-tank, generally by pumping compressed 
air into the top of the closed vessel; the latter is then opened, the wood is with¬ 
drawn, and the whole operation is then repeated. The total time occupied varies 
from three to twelve hours at the numerous works which employ this pressure 
process. 

Creosoting has been found to be the best of all the preservatives. It is the only 
one effective—when well done—against the sea-worms (Teredo navalis and Lim- 
noria terebrans) which feed on timber, but it is also the most expensive. The gen¬ 
eral practice is to inject from 8 to 10 pounds to the cubic foot in timber to be subse¬ 
quently exposed merely to the weather, and from 10 to 20 pounds to the cubic foot 
in timber to be exposed to sea-worms. The quantity used varies with the activity 
of the worms, those dwelling in southern waters being apparently more voracious 
than those in northerly ports, and feeding on the wood all the year round instead 
of hibernating. As creosote costs, generally, about one cent a pound in the United 
States, the total cost of creosoting, when well done, may be estimated at from twelve 
to sixteen cents a cubic foot (from thirty-six to forty-eight cents per tie of 3 cubic 
feet) for timber to be exposed to the weather, or at from fourteen to twenty-four 
cents a cubic foot (from $12 to $20 per 1000 feet board measure) for timber to be 
exposed to marine worms. Prices are somewhat cheaper in Europe in consequence 
of cheaper creosote, and this process is exclusively used in England, where the 
numerous gas-works afford cheap coal-tar. 

As it has been found injurious to cut into the wood after treatment, thus remov¬ 
ing the outer protection, which is the most effective, timber is generally framed 
before creosoting. Enormous cylinders, 12^ ft. in diameter and 22 ft. long, are used 
in England for creosoting the entire bodies of freight-cars after they have been 
assembled. 

Creosote is distilled from coal-tar and contains a number of tar acids (carbolic, 
cresylic, acridine, etc.), which are powerful antiseptics, in solution with a thick, 
gummy, insoluble oil containing naphthaline. It thus acts chemically by poison¬ 
ing the germs of decay, and mechanically by repelling the intrusion of moisture. 
The amount absorbed and the consequent benefits conferred vary with the character 
and density of the wood, but it may be said', in general terms, that timber and rail¬ 
road ties, properly creosoted, will last from eight to twenty years, and that creosoted 
piles, exposed to sea-worms, will last from ten to twenty years, if the work be well 
done and the creosote be of good quality. The temptation to do poor work or to 
buy cheap creosote is, however, very great, for the material is expensive. In the 
early days all sorts of patented processes were introduced to diminish the quantity 
used, such as injecting the timber with cold creosote instead of hot, which is more 
limpid, limiting the pressure and time of treatment, treating with vapors instead of 
oil, etc., but these have all given bad results and are abandoned. 

The mode of application in burnettizing is much the same as in creosoting, 
except that the solution is more frequently admitted at atmospheric temperature, 
instead of being heated. The chloride of zinc is obtained by pouring hydrochloric 


778 


APPENDIX. 


acid upon metallic zinc in a lead-lined vat, thus forming zinc chloride. The process 
may be hastened by steaming, and the resulting solution is about 50 per cent strong. 
Care must be taken to obtain a saturated solution, as free acid injures the strength 
of the wood, even when reduced to the 1.50 to 3 per cent solution which is injected. 

Various species of wood differ greatly in their receptive qualities, some absorb¬ 
ing 50 per cent more solution than others. It is, therefore, advisable to select for 
treatment the more open-grained, porous woods, provided they have sufficient hard¬ 
ness to withstand the intended wear. It may be said, in general terms, that 
black and red oak, mountain pine, hemlock, and beech receive burnettizing well 
and are greatly benefited by it. White and burr oak, chestnut, yellow pine, or 
spruce are too close-grained and should not be treated; they are durable woods 
generally and but little sap can be extracted from them. 

Great care has to be exercised in regulating the strength of the solution injected. 
If it be too strong the wood will be made brittle, and if it be made too weak the 
zinc will wash out in time and leave the timber unprotected. In Germany, where 
burnettizing is all but universally used for railroad ties, the best results are said to 
have been obtained with solutions 1.90 per cent strong, while in the United States 
solutions 3.75 and 5 per cent strong rendered the ties “as brittle as carrots.” The 
aim should be to have the wood contain at least one quarter of one per cent of zinc 
chloride of its own weight when dry. For this purpose it is advisable to vary the 
strength of the solution from time to time, in accordance with the condition of the 
wood, for when freshly cut it takes in far less of the liquid than when dry. How 
much it will absorb when in the latter condition may be realized from the fact that 
31,006 mountain-pine ties, treated in August, drank up 1,679,289 pounds of solu¬ 
tion, an average of 54 pounds per tie, or 9 tons per average cylinder-full of 333 ties. 
The zinc absorption was in that case 0.65 of one per cent of the weight of the 
wood, although the solution was only 1.46 per cent strong. 

For bridge work burnettizing has been found to render the timber unduly 
brittle, particularly for those pieces exposed to tensile or to cross strains, but for 
railroad ties it has given results, under favorable circumstances, but little inferior 
to creosoting. It lengthens the life of various species of wood, which would other¬ 
wise decay in the track in from three to five years, to a life of from eight to eighteen 
years, varying somewhat with the exposure and with the individual ties. This 
results probably from the difference in density of individual trees, as determined by 
their exposure and soil, for upon weighing a lot simultaneously cut from the same 
forest and seasoned in the same way, just before and just after treatment, the 
differences in absorption were found to range from 13 per cent to 80 per cent of the 
■weight of the ties. The result is that preserved ties do not all give out at once, 
like those in their natural state, but that some show a longer life than others. The 
principal difficulty with burnettizing is that the zinc, being a very soluble salt, is 
apt to wash out of the wood when placed in a wet exposure. A number of devices 
have been resorted to for the purpose of preventing this. 

In the United States a process has been introduced in which two solutions are 
used. The first consists of zinc chloride to which a little gelatin has been added, 
and when the wood has been impregnated with this a second solution of tannin is 
introduced and forced into the wood. The gelatin and the tannin, coming into 
contact, form insoluble pellicles of artificial leather, which act as diaphragms and 
so prevent the zinc from being washed out. Several millions of ties have been pre¬ 
pared by this process within the last nine years, and it seems to be giving satisfac¬ 
tory results. 

In Germany, reasoning from the fact that the effectiveness of creosote results 
from the combination of antiseptics with an insoluble oil which repels moisture, a 
process has been introduced in which an aqueous solution of chloride of zinc is 
mixed with about 8 per cent of creosote. As water and oil will not dissolve each 
other, the result is not a solution, but an emulsion, and mechanical means have to 
be adopted to keep the two intimately mixed. The process is said to be a success, 
but if a true chemical solution could be obtained of some of the metallic antiseptics 
with a cheap oil, such as petroleum, it is probable that still better results would be 
obtained. Efforts have been made by chemists to compass such a solution, but thus 
far without success. 


PRESERVATION OF WOOD. 


779 


The cost of burnettizing varies from four and one-half to seven cents per cubic 
root, or say from fourteen to twenty cents per railroad cross-tie, in accordance with 
the process adopted, the kind of wood selected, and local circumstances. It is thus 
seen to cost less than half as much as creosoting, and to give results but little in¬ 
ferior, except in the case of timber exposed to sea-worms, where creosoting alone 
has proved a specific. 

As already intimated, corrosive sublimate and sulphate of copper are now but 
little used. There are still in Europe and in the United States a few establishments 
working with these antiseptics or with some processes which are on their trial, but 
they are not numerous and are not increasing in number. For work to be done 
upon ci large scale the choice lies , practically, between creosotin g and burnettizing , 
including therein the various modifications in the mode of application of these pre¬ 
servatives. 

The principal scope for the preservation of wood lies in its application to railroad 
ties. For this it has proved thoroughly effective, and there is no longer any ques¬ 
tion of its economy in Europe, so that railway managers there who fail to avail them¬ 
selves of it are alluded to as neglecting an important economy. In the United 
States there are as yet few railroads which resort to such treatment. This results 
from the comparative prices of the untreated ties. In Europe they cost from sixty 
cents to one dollar each, while in the United States the first cost is from twenty-five 
to seventy-five cents each, in consequence of the present abundance of timber. 
There are many roads, however, upon whose lines the more durable woods have been 
so far exhausted that the inferior woods can be procured and treated at a less ag¬ 
gregate cost than the white oak, burr oak, and chestnut which have thus far con¬ 
stituted the tie supply. The necessity for doing this has, for a time, been retarded 
by opening up new sources of supply in the extension of other railroads, or the ship¬ 
ping of ties from forests contiguous to navigation ; but it is very evident that even 
these supplies wall be exhausted after a time, and that there will be an increasing 
number of railroads which will find an economy in resorting to wood preservation. 

Such roads should first endeavor to have the inferior, cheap, and perishable wrnods 
treated, both because they have been found to absorb antiseptics best and because 
they will be cheaper. When white oak ties cost 53 cents each, and hemlock 30 cents 
each, unprepared, the latter, if burnettized, will procure an economy of about $100 
a year per mile of track maintained. There were, at an early day, numerous fail¬ 
ures with even the best processes, but these have gradually been traced to their causes, 
and there is now no question as to the results which can be accomplished. It is 
necessary, how r ever, that the treatment should be well and skilfully done, for there 
are many idiosyncrasies in the various species of wood which require experience to 
get the best results. Allusion has already been made to the fact that care is taken 
to select the proper species for treatment; lo the care which should be taken to ascer¬ 
tain the condition of the w 7 ood, so as to vary the strength of chemical solutions or the 
length of the treatment accordingly ; and to pay attention to the differences which 
exist in the receptivity of individual trees. To this it may be added that most woods 
should be allowed to season, if at all practicable, before treatment, but that in some 
species the resulting evaporation of the moisture from the sap leaves the latter haul 
and gummy, thus resisting absorption; and that it is very desirable to allow ilie 
treated ties to dry out as much as possible before laying them in the track, so as to 
remove the watery portions of the solution ; also that if decay has already begun 
the wmod should not be treated at all. It will then absorb the solution copiously, 
but the decay will proceed much more rapidly than it dees in sound treated ties. 

Much depends also upon the time at w r hich the wood is cut. In northern latitudes 
it is best to cut in the winter, and this is now the general practice, while in southern 
latitudes it is said that it is best if cut in the autumn, the reason in both cases be¬ 
ing the same, that the period should be selected in which, either from the cold in the 
north or the dryness of summer in the south, there is the least quantity of perish¬ 
able sap in the wood. Those curious on the subject will find many data and records 
of experiments in a report made by a committee on the preservation of timber to 
the American Society of Civil Engineers, and published, together with the discus¬ 
sions on it, in the transactions of that society for July, August, and September, 1885. 
This sets forth, at considerable length, the results of American experience, as well as 


780 


APPENDIX. 


the conditions of success, and has since been reinforced by a number of interesting 
bulletins from the Forestry Division of the United States Department of Agriculture, 
calling attention to the relation of railroads to the forest supplies, and inculcating 
various methods of promoting economy. 

The time has not yet arrived when any economy will accrue from the use of 
metallic ties in the United States. If made of adequate strength the annual interest 
on the outlay will amount to more than the annual renewal oi wooden ties, partic¬ 
ularly if the latter are chemically preserved. 


INDEX 


j^Lbrasion tests of stone, results of, 645 
Absorption test of stone, 636 
Acid and basic open-hearth processes com¬ 
pared, 142 

Added material on one side of member, 
effects of, 36 

Adhesion of natural to Portland cement, 
598 

Adhesion tests of cement, 449 
Adhesive force of nails in oak wood, 689 
Adhesive strength of cement-mortars to 
various substances, 597 
Age (in storage), effect of, on the strength 
of cement, 593 
Albert-lay of wire rope, 701 
Alloys, the manufacture of the more use¬ 
ful : 

nature of metallic alloys, 173 
the copper-zinc-tin alloys, 174, 550, 552 
the brasses—copper aud zinc, 176, 550 
Delta-metal, 177, 56'*' 

Tobin bronze, 178, 554, 556 
the bronzes—copper and tin, 178, 550, 
565 

phosphor bronze, 178, 554, 556 
silicon bronze, 179 
aluminum bronze, 179, 555, 556 
hardened aluminum, 180 
fusible alloys, 180 
Aluminum : 

general properties of, 173 
how hardened, 180 
in steel, 180 
Aluminum bronze : 
how made, 179 
strength of, 555 

Angular deformation under direct stress, 
6 


Annealing copper wire and plate, 550 
Annealing steel, 146, 153, 168, 170, 731 
effect of, on strength qualities, 498, 
501 

Annual rings in wood, 207 
Apparent elastic limit, 12, 18, 309 
Areas of contact between car-wheels and 
rails, 506 

Ash (species of) in the U. S., 279 
Aspen in the U. S., 281 
Autographic stress-diagram apparatus, 34T 
Axles : 

steel, tested by cold bending, 517 
wrought iron and steel, temperature- 
tests on, 563 

13acli’s compressometer, 355 
Bach’s tests on concrete columns or 
prisms, 601 

BaclS’s comparative analysis of recommen¬ 
dations of the Conventions and of the 
French Commission, 737 
Basic and acid open-hearth processes com¬ 
pared, 142 

Basswood in the U. S , 281 
Bauschinger, Prof. Johann, biographical 
sketch of, 723 

Bauschinger’s mirror extensometer, 342 
Beams —see Cross-bending stress. 

Beams, wooden : 

tables of strength of, 681, 682 
effect of size on strength of, 672 
Concrete and iron, strength of, 72 
Beech in the U. S., 282 
Bending, cold —see Cold bending. 

Bessemer and open-hearth steel compared i 
142 

Bessemer process of making steel, 133. 

781 . 




782 


INDEX. 


Billet tests of steel, valuable, 502 

Birch in the U. S., 282 

Bleeding Southern pine, effects of, 672 

Boiling test of cement, 417 

Brard’s process —see Sulphate-of-soda test. 

Brass, strength of, 550 

Brasses, the manufacture of, 176 

Brick, building : 

strength and elastic properties of, 651, 
662 


strength of brick piers, with stress-dia¬ 
grams, 651-659 

Brick, “ vitrified,” (for street-paving:) 
definition of, 196 

clays employed in manufacture of, 197 
physical properties of clays for, 198 
preparation of the clays, 200 
moulding the brick, 201 
drying and burning, 202 
annealing after burning, 203 
sorting the brick, 204 
kinds of tests required, 456 
the cross-breaking test, 457 
the crushing test, 457 
the rattler test, 457, 460 
standard tests of the Nat’l Brick 
Mfg. Assoc., 460 
results of tests, 660 
Brick piers, strength of, 651-659 
Briquettes, cement : 
forms of, 432 

form proposed by author, 434 
distribution of stress in, 435 
Brittle and plastic materials, 24 
Brittle materials in compression, 24 
Bronzes, strength of, 550-556 
Buckeye (horse-chestnut) in the U. S., 283 
Building-brick, results of tests of, 660, 662 
'hirniug of cements, 187, 194 

tests for thoroughness of, 413 
hitternut-trees in the U. S., 284 

iP 

V^alcining of Portland cement, 187, 194 
Callipers, micrometer, 350 
Car-axles, strength, of, affected by temper¬ 
ature, 564 
Carbon : 

in cast iron, 91 
in iron and steel, 151 
change in, at a low j^ellow heat, 153 
effect of, on the tensile strength of 
steel, 156, 491-495 


Carbon, effect of, on ductility, 158, 491- 
495 

Carbonic-acid gas, effects of, on the hard¬ 
ening of natural and slag cements, 597 
Cast iron : 

historical account of, 87 
general properties of, 90 
carbon in, 91 
silicon in, 92 

influence of, on mechanical prop¬ 
erties, 94 

influence of, on shrinkage, 95 
sulphur in, 97 
phosphorus in, 97 
manganese in, 98 
pig-iron, grading of, 99 
foundry practice, 100 
the cupola, 100 
effect of remelting, 101 
the moulds, 102 
moulding sand, 104 
effect of size and shape, 105 
pipes and columns, 480 
shrinkage, 105 
shrinkage stresses, 477 
the mechanical properties of, 106 
hardness, 106 

hardness and strength, 107 
crushing strength, 77, 473 
transverse strength, 109, 475 
transverse deflection, 372 
modulus of elasticity of, 476 
tensile strength, 110, 469 
Kirkaldy’s results, 477 
strength measured by shocks, 480 
malleable cast iron, 112 
defined, 112 

method of manufacture, 113 
mechanical properties of, 114 
magnetic testing of, 701 
Catalpa-trees in the U. S., 284 
Cedars of the U. S., 267 
Cellulose from wood, 249 
Cement, natural : 

manufacture described, 182 
strength of, 568 
mortar of : 

with different proportions of 
sand, 579 

strength of, at various periods, in 
terms of its strength at 28 days, 
573 










INDEX. 


783 


Cement, natural: 
mortar of : 

hardening iu air and in water, 
576-7 

effect of regauging after set begins, 
593 

effect of carbonic acid gas on the 
hardening of, 597 
effect of freezing on, 613 
effect of salt on, 617-621 
adhesive strength of, 597 
effects of long storage on the 
strength of, 593 
Cement, Portland : 

historical account of, 183 
ingredients of, 185 
cla} r s for, 185 

silica and its compounds, 186 
alumina for, 186 
sulphur compounds in, 187 
chemical reactions in calcining, 187 
explanation of the setting and harden¬ 
ing, 189 

sources of the raw materials for, 191 
pulverizing and mixing the raw ma¬ 
terials, 192 

processes used in burning, 194 
grinding the clinker, 195 
strength of, 572 

modulus of elasticity of mortars, 575, 
601 

hardening in air and in water, 576-7 
mortar of : 

with different proportions of sand, 
579 

with different sizes of sand-grains, 
582 

economy of coarse and fine sands, 
587 

relations between strength and 
cost, 606 

porosity of, for different sands, 591 
strength of, at various periods, in 
terms of its strength at 28 days, 
573 

compressive strength and elas¬ 
ticity of, 603 
economy of, 605 
effects of freezing on, 612 
effects of salt on, 617-621 
long storage, effect of, 593 
regauging, effect of, on strength, 593 


Cement, Portland : 

adhesive strength of, 597 
concretes, 3 

strength and elasticity of, 601 
economy of, 605 

Wheeler’s tests of concrete beams, 
608 

filtration through, 612 
mixtures, volumes of, 608, 623 
in sea-water, 623 

fire-resisting properties of various 
mixtures, 626 

cinder concretes, cost and proper¬ 
ties of, 627 

Cement, slag —see Slag-cement. 

Cement-testing : 

standard tests, 407 
fineness of grinding, 409 
thoroughness of burning, 413 
rate of setting, 415 
tests for soundness, 417 
the boiling test, 417 
tensile-strength tests, 419 
fixed relation between tensile and 
compressive strength, 419 
standard consistency of briquettes, 420 
standard sand to be used, 424 
standard consistency of cement-mor¬ 
tars, 429 

formation of the briquettes, 430 
Bohme’s hammer, 432 
Tetmajer’s apparatus, 433 
form of the briquette, 432 

standard American and English 
form, 433 

standard German form, 434 
form proposed by t lie author, 434 
distribution of stress over mini¬ 
mum section, 435 
moulds for briquettes, 438 
clips, their bearings and mountings, 

438 

the author’s design, 440 
tension-test machines, 440 

standard German form, 441 
Fairbanks’ machine, 441 
Riehle’s machine, 443 
Olsen’s machine, 444 
Porter’s machine, 445 
rate of applying the load, effect of, 
442 

eccentric position in the clips, 446 



784 


INDEX ; 


Cement-testing : 

compression tests of cement, 446 
Swiss machine for making, 448 
cross-bending tests, 448 
adhesion tests of cement, 449 
form of adhesion briquette, 450 
variations (normal) of volume in air 
and in water, 451 
French Commission recommenda¬ 
tion, 452 

permeability test, 452 
decomposing action of sea-water, test 
for, 454 

Cement-testing machines, 440 
Centre-punch, double-pointed, 352 
Chains, strength of wrought-iron, 489 
Changes in the elastic limits by stressing 
beyond these limits, 522 
Charcoal, 248 

Chemical analysis not adequate to explain 
mechanical qualities of steel, 150-154 
Chemical composition of wood, 246 
Chemical constituents, limiting values al¬ 
lowable in steel, 167 
Chemical tests of stone, 635 
Cherry-trees of the U. S., 285 
Chestnut-trees of the U. S., 285 
Cinder-concrete mixtures, strength and 
economy of, 627 

Cinder-concrete w T ith metal base, strength 
of, 629 
Clays : 

for Portland cement, 185 
for paving-brick, 197 
Cleavability of wood, 243 
Clinker-cement, 187, 195 
Clips for cement briquettes, 438 
the author’s design, 440 
Coarse particles in cement have no cement¬ 
ing quality, 409 
Cotfee-trees of the U. S., 286 
Cold-bending tests : 

character aud significance of, 394 
methods of making, 395 
preparation of the specimen, 397 
comparison of results from, with those 
from tension tests, 399 
combined specified requirements in 
tension and cold bending, 402 
comparison of results from tension, 
impact, and cold bending, 
403 


Cold-bending tests: 
of steel axles, 518 
of steel wire, 697 
Columns: 

cast-iron, defects in, 481 
effect of the addition of material to 
one side of, 36 
eccentric loading on, 36 
tests of, 359 
strength of, 360 

Consideire’s results, 361 
Tetmajer’s results, 364 
formulae for, 366 
Columns, wooden : 
tests of, 682-689 
formulae for, 683-4 

Composite (concrete and steel) beams com* 
puted, 72 

Compression-members —see Columns. 
Compression tests, 24 

two classes of materials, 24 
on plastic materials, 24 
on brittle materials, the laws of, 24 
angle of rupture found, 25 
relation of crushing strength to 
shearing strength, 28 
relation of strength to form of 
specimen, 29 

relative strength of prisms and 
cubes, 31 

effect of loading a portion of the 
surface, 32 

test-specimens for, 353 
bedding of specimens in the test¬ 
ing-machine, 354 
eccentric loading, 36 
effect of material added to one side of 
column, 36 

compression testing-machines, 355 
compressometers, 355 
Olsen’s, 355 
Bach’s, 355 
the author’s, 357 
Tetmajer’s, 359 
tests of columns, 359 
compressive strength of columns the 
same as the “apparent elastic 
limit,” 360 

Considere’s mounting for column tests, 
361 

Considere’s results of column tests, 362 
Tetmajer’s “ “ “ “ 364-5 




INDEX. 


785 


Compression tests : 

ultimate strength formulae for col¬ 
umns, 366 

spring testing-machines, 367 
compression tests of cement, 446 
Swiss machine for making, 448 
on cast iron, 77, 473 
on steel, 502-509 

Compressive strength of cement-mortar as 
related to its tensile strength, 419 
Compressometers, 355 
Concrete (see also Portland cement and 
Natural cement): 

compressive strength and elasticity of, 
603 

economy of various mixtures, 605 
volumes “ “ “ 608 

Concrete and steel in combination, strength 
computed, 72 

Concrete beams, mixtures and strength of, 
608 

Concrete mixture, absolute volumes in, 623 
Concrete structures in sea-water, 623 
Conductivity, electrical, table of, 721 
Consistency of cement mortars in test bri¬ 
quettes, 420, 429 

Conventions, comparative analysis of 
recommendations of, 737 
Copper: 

general properties of, 172 
strength of, 548, 566 
annealing of, 550 
Corrosion of iron and steel, 171 
Cottonwoods of the U. S., 298 
Cross-bending strength of timber ex¬ 
plained, 236 
Cross-bending stress: 

historical sketch of theories, 42 
fundamental equations of equilibrium, 
44 

relation between moment of resistance 
and stress on extreme fibre, 46 
noment of resistance of various forms, 
48 

moment of resistance beyond the elas¬ 
tic limit, 49 

distribution of stress and position of 
neutral axis at rupture, 50 
moduli of rupture in cross-breaking, 
51 

-distribution of shearing stress in a 
beam, 52 


Cross-bending stress : 

beams proportioned for shearing 
stress, 56 

deflection of beams—general formu¬ 
lae, 57 

beam fixed at one end and loaded at 
the other, 59 

beam supported at the ends and loaded 
at the centre, 60 

beam supported at the ends and uni¬ 
formly loaded, 61 

table of moments, stresses, and deflec¬ 
tions, 61 

deflection from shearing forces, 66 
determination of Young’s modulus of 
elasticity, 67 

the rational designing of flitclied 
beams, 68 

composite concrete and steel beam, 72 
flat plates uniformly loaded, 73 
resilience of beams, 83 
Cross-bending tests 
objects of, 369 
essential conditions of, 369 
machines for, 370 

deflection essential when testing cast 
iron, 372 

computed strength] in pounds per 
square inch, 373 

modulus of elasticity (stiffness), 374 
of cast iron, 109, 475 
of cement, 448 

Crucible process of making steel, 133 
Crushing —see Compression. 

Crushing strength a function of shearing 
strength, 28 

Crystalline fractures in wrought iron, the 
causes of, 120 

Cubes and prisms, relative strength of, 31 
Cucumber-tree, 301 

Cutting up logs in the U. S. timber tests, 
464 

Cylinders on planes, elastic-limit loads of, 
508 

Cypress of the U. S., 269 

Decay of wood : 

produced by fungus-growth, 250 
prevention of, 252 

Decomposing action of sea-water on cement- 
mortar, test of. 454 
Defects, microscopic, in steel, 537 



7SG 


INDEX. 


Deflection of beams, 57 
table of, 61 

from shearing forces, 66 
Deformation : 
defined,2 
various kinds of, 4 

longitudinal and lateral, under direct 
stress, 5 
of volume, 5 
significant limits of, 306 
Deformation, angular, under direct stress, 6 
Delta-metal : 

strength of, at various temperatures, 
566 

how made, 177 

Distillation products of wood, 248 
Distribution, geographical, of the Southern 
pines, 684 
Drifting tests: 

their character and significance, 406 
specification for, 406 
Drying timber, 224, 676 
Durability of wood, relative, of different 
species, 250, 253 

^Eccentric loading, effects of, 36 
Eccentric position of briquette in clips, 
effects of, 446 

Economy of cement-concrete mixtures, 
605, 627 

Elastic and plastic bodies defined, 1 
Elastic field destroyed by overstraining, 
522 

Elastic limit : 

defined, 18, 306 

absolute limits unsatisfactory, 308 
the “apparent elastic limit,” 12, 18, 
309 

of wrought iron in tension, 486 
of wrought iron after stressing beyond 
the elastic limit, 486-488 
of steel in tension, 491-496 
of steel in compression, 504 
of steel cylinders on planes, 508 
of steel as affected by loading beyond 
the elastic limits, 512, 522 
of nickel-steel, 516 
of timber, 670 

Elastic limits changed by overstraining, 
486, 522 

Electrical conductivity of metals, 721 
Elms of the U. S., 286 


Elongation : 

how distributed in a steel test-speci¬ 
men, 502 

of tension test-specimens, Tetmajer’s 
analysis of, 317 
percentage of, 21 
Emery testing-machines, 328 
Extensometers, 340 

Eactors of safety with timber, 680 
Fatigue of metals: 

fatigue defined, a new definition of¬ 
fered, 537 

micro-flaws in steel, 537 
Wohler’s tests and appliances, 539 
results of fatigue tests, 541 
limits of max. and min. stresses for an 
indefinite number of repetitions, 541 
a new formula for dimensioning, 545 
Filtration through concrete, 612 
Fineness of grinding of cements, signifi* 
cance and tests, 409 
Fir of the U. S., 269 

Fire-resisting qualities of different kinds of 
concrete, 625 

Flat plates uniformly loaded approxi¬ 
mately computed, 73 
Flaws, microscopic, in steel, 537 
Flexibility of wood, 244 
Flitched beams, the design of, 68 
Forging under a light hammer, effects of, 
517 

Form of specimen a function of crushing 
strength, 29 
Formulae : 

for the ultimate strength of columns, 
366, 683 

for dimensioning for repeated loads, 
545 

Foundry practice —see Cast iron. 

Fractured specimens : 
of timber, 241 
of car axles, 563 
of wrouglit-irou and steel, 398 

Freezing, effects of, on cement-mortars, 
613 

Freezing tests of stoue, 633 
French Commission, report of, compared 
with resolutions of the Conventions, 737 
Frictional resistance : 
of riveted joints, 525 
per square inch of rivet area, 527 



INDEX. 


787 


Fuel value of wood, 247 
Fusible alloys, 180 

(jTauging implements, 352 
Geographical distribution of Southern 
pines, 684 

Gneiss —see Granite. 

Grains of wood, 215 
Granites and gneisses: 
structure of, 630, 631 
strength of, 640, 643, 645 
resistance to abrasion, 650 
Gray’s autographic stress-diagram appara¬ 
tus, 346 

Grinding of cement-clinker, 195 
Gripping devices, 324 
Grooved sections, tensile strength of, 514, 
530 

Gum trees of the U. S., 288 

Hackberry-trees of the U. S., 289 
Hardening of cement-mortars in air and in 
water, 576-577 

Hardening, tempering, and annealing of 
steel, 168, 170, 731, 734 
Hardness tests: 

hardness defined, 381 
test for resistance to indentation, 381 
test for resistance to abrasion, 383 
Hardness of timber, 243 
Heart-wood, 207, 255 
Hemlock of the U. S., 271 
Hickory-trees of the U. S., 289 
Holly-trees of the U. S., 291 
Hysteresis, magnetic, of iron and steel, 
101 

I beams and plate girders tested and com¬ 
pared with specimen tests, 518 
Immersion, long, effects of, on the strength 
of timber, 677 

Impact stresses for given deformations, 79 
Impact tests: 

give no absolute results, 80 
objects of, 375 
essential conditions of, 376 
the energy of the blow, 376 
the pendulum test standardized, 377 
impact testing-machines, 379 
compared with cold-bending tests, 403 
Impact tests on car-axles, 564 
Impact testing machines, 379 


Iron (see also Cast iron, Wrought iron, 
and Steel): 

historical account of its manufacture, 
87 

classification of iron and steel, 88 
magnetic testing of, 703 
micrographic analysis of, 725 
structural constituents of, 734 
Ironwood-trees of the U. S , 283 

I^eep’s testing-machine, 380 
Keep’s diagrams of the strength of cast 
iron, 95, 96 

Kennedy’s shearing-test apparatus, 386 
Key to wood species based on wood struc¬ 
ture, 254, 258 

Ijampblack from wood, 249 
Larch (tamarack) of the U. S., 272 
Launhardt’s and Weyrauch’s formulae re¬ 
placed by one new formula, 545 
Lateral deformation under direct stress, 5 
Length of reduced section, effect of, 514 
Lime, hydraulic, 182 
Lime, manufacture of, 181 
Lime-mortar, hardening of, 181 
Limestone and marble: 
structure of, 630, 631 
strength of, 640, 643, 645 
resistance to abrasion, 650 
Limit of elasticity— see Elastic limit. 

Limits of stress for indefinite number of 
repetitions, 541 

Loading, effects of rate of, 305 
Loads suddenly imposed, 81 
Locust-trees of the U. S., 291 
Long storage, effect of, on the strength of 
cement, 593 

Louisville cement, strength of, 569, 570 
Low red heat, effects of finishing steel at, 
499 

IVilachines, testing, general requirements 
for, 304 

Magnetic testing of iron and steel: 
magnetic properties defined, 703 
permeability, 703 
unit of mauetizing force, 703 
unit of magnetization, 703 
hysteresis, 703 

Stein metz law on hysteresis, 
705 




788 


INDEX. 


Magnetic testing of iron and steel: 
methods of testing, 705 

measurement of permeability, 705 
ring method, 706 
divided-bar method, 708 
double bar method, 709 
magnetic-bridge method, 710 
voltmeter method, 711 
permeameter method, 712 
magnetic balance, 712 
measurement of hysteresis, 713 
miscellaneous methods, 713 
ring method, 713 
Ewing’s hysteresis-tester, 714 
results of tests, 716 

development due to testing, 716 
-conditions affecting magnetic quality, 
718 

-conductivity data, 721 
importance of testing, 722 
Magnetization, unit of, 703 
Magnetizing force, unit of, 703 
Magnolia-trees of the U. S., 300 
Manganese: 

in cast iron, 98 
in steel, 161, 162 

Manganese bronze, strength of, at various 
temperatures, 566 

Malleable iron —see Cast iron, 112 ' 

Maple-trees of the U. S., 291 
Marshall’s extensometer, 340 
Martel’s law of indentations, 382 
Mechanical properties of timber, 133 to 
245 

Mechanical tests in general, 302 
classification of, 303 
Micro-flaws in steel, 537 
Micrographic analysis of iron and steel, 725 
Micrometer-callipers, 350 
Microscopic tests of stone, 635 
Milwaukee cement, strength of, 569 
Modulus of elasticity (Young’s): 
defined, 3 

of volume under direct stress, 6 
for shearing stress, 8 
determination of, from beam deflec¬ 
tions, 67, 374 
of cast iron, 476 
of wrought iron (Fig. 392), 483 
of steel, 509 

independent of other qualities in steel, 
510 


Modulus of elasticity (Young’s): 

of cement-mortars and concretes, 575, 
601, 602, 603 
of timber, 670 
Moisture in timber, 676 
distribution of, 223 
test for, 667 
reabsorbed, 668 

effects of, on strength, 242, 667 
Molecular structure of wrought iron and 
steel, 144 

Moments of inertia of various forms, 48 
Moments of resistance of various forms of 
beams, 48 
Mortar, cement: 

hardening in air and in water, 576-7 
strength of, for different proportions of 
sand, 579 

strength of, for different sizes of sand- 
grains, 582 

strength of, at various periods as com¬ 
pared with the strength at 28 days, 
573 

economy of coarse and fine sands, 587 
with artificial compositions of sand 
589 

porosity of, as dependent on the sand 
used, 591 

adhesive strength of, 597 
compressive strength and elasticity of, 
603 

economy of, 605 
effects of freezing on, 613 
anti-freezing mixtures, 615 
rates of setting at dilferent tempera¬ 
tures, 616 

effects of salt on, 617-621 
fire-resisting properties of various mix¬ 
tures, 626 
Mortar, lime : 

hardening of, 181 
Moulds for cement briquettes, 438 
Muck bars, 122 

Mulberry-trees of the U. S., 293 

^Nails, holding-force of, in oak wood, 689 
Natural cement —see Cement, natural. 
Nickel-steel, 515 

Oak-trees of the U. S., 293 
Olsen’s testing-appliances: 
testing-machines, 320 





INDEX. 


789 


Olsen's testing-appliances: 

stress-diagram apparatus, 349 
compressometers, 355 

Opeu-heartn and Bessemer steel, com¬ 
pared, 142 

Open-hearth process of making steel, 138 
Osage-orange trees of the U. S., 298 
Outerbridge’s experiments on increasing 
the strength of cast iron, 480 
Overstraining destroys the elastic field, 522 
Overstrained metal restored by annealing, 
513 

aving-brick— see Brick, vitrified. 
Paving-brick tests, 456 
cross-breaking, 457 
crushing, 457 
rattler test, 457, 460 
general table of results, 660 
Pendulum impact testing-machines, 377 
Permeability, magnetic, of iron and steel, 
703 

Permeability (to water), test of cement- 
mortars for, 452 

Persimmon-trees of the U. S., 298 
Phosphor-bronze : 
how made, 178 
strength of, 554, 556 
Phosphorus: 

in cast iron, 97 

in wrought iron and steel, 165-7 
in bronze, 178, 554, 556 
Photomicrographs of steel, 736 
Pig iron, grading of, 99 
Pillars —see Columns. 

Pines of the United States : 
soft, 274 
hard, 275 

Pine, short-leaf and long-leaf, identified by 
geographical distribution, 684 
Pipes, cast iron, with uusymmetrical thick¬ 
ness, 481 

Plastic and elastic bodies defined, 1 
Plastic and viscous materials, 24 
Plastic materials in compression, 24 
Plate girders, tests on. 518 
Plates, flat, strength of, 73 
Poisson’s ratio defined and values given, 5 
Poplar-trees (see also Tulip), 298 
Porosity of mortars as dependent on the 
quality of the sand used, 591 
Portland cement —see Cement, Portland. 


Posts —see Columns. 

Preservation of timber, 775 
Prisms and cubes, crushing strength of, 31 
Puddling process, 117 
Punching and shearing, injurious effects 
of, 532 

Punching tests of steel not valuable, 500 
Puzzolana cement —see Slag-cements. 

C^uenchiug and annealing, effects of, on 
low-carbon steel, 500 

flails, car-wheels on, 506 
Kate of applying load : 

effects of, in general, 305 
effect in cement-testing, 442 
Rattler test of paving brick, 457, 460 
Reduction in the rolls, effect of: 

on strength of wrought-iron, 131, 483 
on strength of steel, 496-498 
Reduction of area in tensile tests, 23 
Reduction of area on steel test-specimens, 
502 

Regaugings after set has begun, effect of, 
on strength, 593 
Resilience : 
defined, 75 

stored in elastic bodies, 76 
a measure of the body to resist shock, 
76 

areas of stress-diagrams, 82 
of bodies under direct stress, 83 
in cross-bending, 83, 3/2 
in torsion, 85 

comparative, for different stresses, 86 
of cast iron, 478 
Resin from wood, 249 
Resonance of wood, 218 
Riehle’s testing-machines, 320, 327 
Rivet-steel, stress-diagram of, 496 
Rodman’s apparatus for testing hardness 
standardized, 296 
Rope, wire —see Wire rope. 

Rosen dale cement, strength of, 568 
Russell’s impact testing-machine, 380a 
Rusting —see Corrosion. 

Salt, effect of, on cement-mortars, 617-621 
Sand in cement-mortars: 

standard to be used in cement tests, 424 
effect of different sands on the strength 
of cement-mortar, 424 




790 


INDEX. 


Sand in cement-mortars: 

effect of increasing proportions, 579 
“ “ varying sizes, 582 

“ “ composition, 587, 589 

Sand-cement, strength of mortar of, 576 
Sandstones : 

structure of, 631, 632 
strength of, 639, 640, 643, 645 
resistance to abrasion, 650 
Sap-wood, 207, 255 
Sassafras-trees of the U. S., 300 
Scarfed joints, how to avoid, in riveted 
work, 533 

Sea-water, effect of, on cement-concretes, 
623 

Setting of cement, 189 
rate of, 415 

automatically recorded, 415 
retardation of, at low temperatures, 616 
Shaft 16 in. diam. forged under a light 
hammer, 517 

Shafts, steel, drawn through dies, 518 
Shearing modulus of elasticity, 8 
Shearing and direct stresses, 7 
Shearing and punching, injurious effects 
of, 533 

Shearing strength : 

governs crushing strength, 28 
of wrought iron, 485 
of steel, 525 
of timber, 240 
Shearing stresses : 
cases of, 38, 385 
in beams, 52 
Shearing tests. 

essential conditions of, 385 
appliances for making, 386 
of wrought iron, 485 
of steel, 525 

Shock-resistance measured by resilience, 
76 

Shrinkage of timber • 
explained, 227 
effects of, 229 
amount of, 232 
Sifting cement, 410 
Silicon : 

in cast iron, 92 

influence of, on mechanical properties, 
74 

influence of, on shrinkage, 95 
on iron and steel, 160 


Silicon bronze, how made, 179 
Size of wooden beams—effects of, on 
strength, 672 
Slag-cements : 
described, 190 

long storage, effect of, on strength, 594 
effect of carbonic-acid gas on, 596 
Slipping of riveted joints, 527 
Soundness test of cements, 417 
Specifications for iron and steel: 

of American Society of Civil Engi¬ 
neers, 756 

of Mr. H. H. Campbell, 756 
of American steel manufacturers, 767 
Specific gravity: 
of cements, 413 
of wood, 219 

of different species of timber, 222 
of stone, 637 

Spring and summer wood, 208 
Spring testing machines, 367 
Spruces of the IT. S , 277 
Standard tests of paving-brick, 460 
Steel: 

methods cf manufacture, 133 
the crucible process, 133 
the Bessemer process, 133 
the open-hearth process, 138 
comparison of basic and acid open- 
hearth processes, 142 
comparison of Bessemer and open- 
hearth steel, 142 

molecular structure of wrought iron 
and steel, 144 

fracture showing structure, 145 
as affected by heat treatment, 146 
mechanical qualities of steel of various 
grades, 147 

not fully explained by its chemi¬ 
cal composition, 150 
influence of carbon on iron, 151 

combination of carbon with iron, 
151 

found in three forms, 151 
change in the carbon at a low yel¬ 
low heat, 153 

hardeningand tempering steel, 153 
chemical analyses cannot explain 
mechanical effects, 154 
the hardening of steel, 155 
effect on the tensile strength. 
156 



INDEX . 


791 


influence of carbon on iron : 

auxiliary effects of phosphorus, 
sulphur, and manganese, 157 
effect on ductility, 158 
elongation and tensile strength, 159 
modulus of elasticity, 160 
the compressive strength, 160 
hardness and fusibility, 160 
influence of silicon on iron and steel, 
160 

influence of manganese on iron and 
steel, 161 

of small percentages, 162 
manganese steel, 162 
influence of sulphur on iron and steel, 
163 

on red shortness, 163 

on tensile strength and ductility, 

164 

influence of phosphorus on iron and 
steel, 165 

conditions of phosphorus in iron, 

165 

effect on ductility, 166 
effect on static strength, 167 
limiting value of chemical constituents 
allowable, 167 

hardening, tempering, and annealing, 
168 

heat-changes in carbon steel, 168 
hardening, 169 
tempering, 169 

effects of hardening and temper¬ 
ing, 169 
annealing, 170 

corrosion of iron and steel, 171 
strength of, in tension and compres¬ 
sion, 490 

as influenced by carbon, 491-495 
of rivet-steel, 496 
as affected by thickness of plate, 
496-8 

as affected by annealing, 498, 501 
as affected by finishing at a low red 
heat, 499 

as determined by punching tests, 
500 

as affected by quenching and an¬ 
nealing, 500 

as determined by the trial-billet 
test, 502 


Steel : 

elongation, how distributed in the ten¬ 
sion test, 502 

reduction of area in the tension test, 502 
compressive strength in the elastic 
limit, 502 

elastic limit in compression, 504 
areas of contact between car-wheels 
and rails, 506 

elastic-limit loads of cylinders on 
planes, 508 

moduli of elasticity in tension and 
compression, 509 

moduli of elasticity independent of 
other qualities, 510 

effect of stressing beyond the elastic 
limit, 512, 522 

over-stressed metal restored by anneal¬ 
ing, 513 

effect of varying the length of speci¬ 
men, 514 
nickel-steel, 515 

effect of forging and rolling, 517 
steel welded tubes, 518 
I beams and plate girders, 518 
variation of moduli with size of I 
beam, 520 

shearing strength, 525 
frictionalresistanceof riveted joints,525 
friction per sq. in. of rivet area, 527 
bearing resistance of plates, 529 
injurious effects of punching and 
shearing, 532 

influence of form of thread in screw- 
bolts, 533 

fatigue tests on, Wohler’s, 539 
micro-flaws in, 537 
magnetic properties of, defined, 703 
methods of testing for, 705 
micrographic analysis of: 
popular account of, 725 
technical treatment of, 728 

constituents of iron and car¬ 
bon steel, 728 

micrographs of steel de¬ 
scribed, 730 

annealing, general influence 
of, on mild steels, 731 
general theory of the structure 
of steel, 734 

structure of hardened steels. 
734 




792 


INDEX. 


Steel : 

photomicrographs of steel, 736 
specifications for : 

by American Society of Civil En¬ 
gineers, 756 

by Mr. H. H. Campbell, 756 
by American steel manufacturers, 
767 

Steel and concrete in combination, strength 
computed, 72 

Steel axles drawn through dies and tested 
in cold bending, 518 

Steinmetz law on magnetic hysteresis, 705 

Stilfness of timber, 234 

Stone: 

crushing test of, 24, 29, 31, 355, 456 
crushing strength of, 637-645 
elastic properties of, 642 
structure of building, 630 
microscopic views of, 631 
“ study of, 635 
weathering of, 632 
freezing tests of, 633 
sulphate-of-soda test, 634 
chemical tests of, 635 
absorption test of, 636 
specific-gravity test, 637 
abrasion, results of tests of, 645 
Bauschinger’s abrasion apparatus, 649 
Stone’s tests of wire and wire rope, 698 
Storage, long, effect of, on the strength of 
cement, 593 

Strain defined as deformation, 2 
Strength moduli of I beams and plate gir¬ 
ders, 520 

Strength of timber, 670-685 
Stress and deformation defined, 2 

proportional, inside elastic limit, 2 
various kinds of, 4 
Stress-diagrams: 

indicate resistance to shock, 81 
for impact and for static loads com¬ 
pared, 79 

autographic apparatus for taking, 344 
Stressing steel beyond the elastic limit, 
effect of, 512 

Stresses from impact and from static 
loads for equal deformations, 79 
Structure of steel, 150, 728 
Structureof wood, 205,209,212,214,254,255 
Structure of wrought iron and steel com¬ 
pared, 144, 728 


Sulphate-of-soda test of stone, 634 
Sulphur : 

in cast iron, 97 

in wrought iron and steel, 163-4 
Sycamore-trees of the U. S., 300 

^Tamarack (larch) of the U. S., 272 
Tannin from wood, 249 
Temperature, effect of, on the time of set¬ 
ting of cements, 408 

Temperature effects on the mechanical 
properties of metals : 
as shown by stress-diagrams, on steel, 
557 

on iron and steel, 557-565 
on copper and bronze, 565 
on delta-metal, 567 

Tensile and compressive strength of 
cement-mortars compared, 419 
Tensile tests . 

general phenomena concerning, 10 
represented by stress-diagrams, 10 
significant points of stress-diagrams, xi. 
the elastic limit in, 11. 18, 306 
the apparent elastic limit, 12, 18, 809 
the yield-point, 12, 18 
significant results of, 17, 312 
modulus of elasticity, 17 
elastic limit, 18, 306 
“apparent elastic limit,” 18, 309 
ultimate strength, 21 
percentage of elongation, 21, 31" 
reduction of area of cross-section, 
23 

selection of the test-specimen, 313 
preparation of the test-specimen, 313 
standard dimensions of test-specimens, 
315 

time-function in, 320 
machines for, 320 

Emery machines, 328 
Olsen machines, 320, 327 
Riehle machines, 320, 327 
cement-testing machines, 440 
gripping devices, 324, 694 
extensometers, 340 

autographic stress-diagram apparatus, 
344 

micrometer callipers, 350 
gauging implements, 352 
compared with those from cold bend¬ 
ing, 403 





INDEX. 


793 


Tensile tests 

of cast iron, 110, 469 
of wrought iron, 481 
of steel, 490-502 
of wire and wire rope, 693 
Testing-machines, general requirements 
for, 304 
Tests: 

mechanical, in general, 302 
classification of, 303 
requirements of machines for, 304 
effect of rate of loading, 305 
significant limits of deformation, 
306 

limits of elasticity, 306 
all absolute elastic limits unsatis¬ 
factory, 308 

the “apparent elastic limit,” 309 
tensile— see Tensile tests, 
compression— see Compression tests, 
cross bending— see Cross-bending tests, 
impact— see Impact tests, 
hardness— see Hardness tests 
shearing— see Shearing tests, 
torsion— see Torsion tests, 
cold-bending— see Cold-bending tests, 
on cement— see Cement tests, 
on stone and brick— see Stone and 
brick tests. 

on timber— see Timber tests, 
on cast iron— see Cast iron, 
on wrought iron— see Wrought iron, 
on steel— see Steel, 
on wire— see Wire and wire rope, 
magnetic— see Magnetic testing of 
iron and steel. 

Test specimens : 

selection and preparation of, 313 
standard forms of, 315 
Tetmajer’s compressometer. 359 
Thickness of rolled forms, influence of, on 
strength qualities, 496-498 
Threads on screw-bolts, influence of the 
form of, 533 
Timber : 

structure of wood, 205, 209, 212, 214 

classification of timber-trees, 206 

sapwood and heartwood, 207 

annual rings, 207 

spring and summer wood, 208 

grains of wood, 215 

resonance, 218 


Timber. 

specific gravity or weight, 219 
variation of weight in a single trunk, 
220 

weights of different species, 222 
moisture distribution, 223, 676 
drying timber, 224 
dry kiln used, 226 
shrinkage of timber explained, 227 
effects of shrinkage, 229 
amounts of shrinkage, 232 
mechanical properties of, 233 

stiffness, or modulus of elasticity, 
234 

cross-bending strength, 236, 468a, 
673 

tension and compression, 238, 468a 
shearing, 240 

methods of failure shown, 241 
influence of weight aud moisture 
on strength, 242, 667, 677 
hardness, 243 
cleavahility, 243 
flexibility, 244 
toughness, 244 
practical conclusions, 245 
chemical composition of wood, 246 
wood as a fuel, 247 
charcoal, 248 

products of wood distillation, 248 
cellulose, 249 

resin, turpentine, and lampblack. 249 
tannin, 249 

durability and decay of wood, 250 
all decay produced by fungus- 
growth, 250 

prevention of decay, 252 
relative durability of different 
species, 253 

identification of different species of 
wood, 254, 684 

examination of the structure essen¬ 
tial, 254 

a structural key to species, 254 
characteristic structural features, 
255 

the use of the key, 257 
key to identification of species, 258 
descriptive list of the more important 
woods of the U. S., 267 
coniferous w T oods, 267 
cedar, 267, 670 





794 


INDEX. 


Timber 

descriptive list of U. S. woods: 
coniferous trees : 
cypress, 269, 670 
fir, 269 
hemlock, 271 
lurch or tamarack, 272 
pine, 273 

soft, 274, 670 
hard, 275, 670, 684 
redwood, 177 
spruce, 277 
bastard spruce, 278 
yew, 279 

broad-leaved woods (deciduous): 
ash, 279, 670 

aspen (see also Poplar), 281 
basswood, 281 
beech, 282 
birch, 282 
blue beech, 283 
bais d’arc —see Osage orange, 
buckeye, or horse-chestnut, 
283 

butternut, 284 
catalapa, 284 
cherry, 285 
chestnut, 285 
coffee-tree, 286 
cottonwood —see Poplar, 
cucumber-tree— see Tulip, 
elm, 286, 670 
gum, 288, 670 
hackberry, 289 
hickory, 289, 670 
holly, 291 

horse-chestnut— see Buckeye, 
ironwood —see Blue beech, 
locust, 291 
magnolia —see Tulip, 
maple, 291 
mulberry, 293 
oak, 293, 670 
osage orange, 298 
persimmon, 298 
poplar and cottonwood (see 
also Tulip), 298 
sassafras, 300 
sycamore, 300 
tulip-wood, 300 
tupelo— see Gum 
walnut, 301 


Timber: 

descriptive list of U. 8. woods : 

broad-leaved woods (deciduous) : 
whitewood— see Tulip, 
yellow poplar— see Tulip, 
tests of the strength of: 

the U. S. timber tests, 462, 664, 
666 

important conclusions drawn 
from, 462, 672, 677 
list of species tested, 463, 665 
method of cutting up logs, 464 
cross-bending test, 465 
crushing endwise test, 467 
crushing across the grain, 468 
shearing test, 468 
tension test, 468 
moisture test, 667, 676 
strength of—results of tests, 664 
as affected by moisture, 667 
tables of strength moduli, 670-675 
effect of bleeding, 672 
effect of time, 468a 
effect of size, 672 

“ “ reabsorbed moisture, 676 

“ “ hot-air drying, 676 

effect of very high temperatures 
and pressures, 677 
effect of long immersion, 677 
effect of varying specific gravity, 
or weight, 677 
factors of safety, 680 
tables of safe loads for wooden 
beams, 468a, 681, 682 
strength of wooden columns, 468a, 
682-689 

identification of sliort-leaf and long- 
leaf pine, 684 

holding-force of nails in wood, 689 
preservation of, 775 

Timber-trees of the U. S., list and descrip¬ 
tion of the most important, 267 
Time-function in timber tests, 468a 
Tin, general properties of, 173 
Tobin bronze : 

how made, 177 
strength of, 554, 556 
Torsion : 

deformation from, 40 
moment of, 39 
resilience of, 85 
tests by, 387 




INDEX . 


795 


Torsion tests : 

contrasted with shearing tests, 387 
machines for making, 387 
Toughness of wood, 244 
Tubes, welded steel, 518 
Tulip-wood trees of the U. S., 300 
Turner’s diagrams of the properties of 
cast iron, 94 

Turner’s apparatus for testing hardness, 384 
Turpentine from wood, 249 

"CJltimate strength in tension, 21 
Use of cement-mortars after set has begun, 
593 

U. S. timber tests : 
described, 4G2, GG4 
species tested, 4G3, 665 
conclusions from, 462, 670-680 
mechanical tests, 465, 664 
Utica cement, strength of, 569 

Yicat’s needle for testing the rate of set¬ 
ting of cements, 416 
Vitrified brick —see Brick, vitrified. 
Volumetric deformation, 5 
Volumetric modulus of elasticity, 6 
Volume variation in cement-mortars, 451 
Vulcanizing process of treating timber, ef¬ 
fects of, on strength, 677 

^alnut-trees of the U. S., 301 
'Water, effect of varying quantities of, on 
the strength of cement, 420 
Weathering of building-stones, 633 
Weight, specific, of timber, 219, 222 
effect of, on strength, 242, 677 
Welded steel tubes, 518 
Welding of wrought iron, 128 
Weyrauch’s and Launhardt’s formulae re¬ 
placed by a new one, 545 
Wheels (car) on rails, areas of contact of, 
506 

Whitewood —see Tulip-tree. 

Wire : 

tests of, 697 

machines for testing, 328, 392, 697, 
698, 699 

strength of, 309, 691, 693, 695 


Wire : 

Stone’s tests of, 698 
Wire rope : 
tests of, 693 
strength of, 695, 700 
methods of laying wire in, 701 
Wohler’s tests and appliances on fatigue 
of metals, 539 
Wood —see Timber. 

Wooden beams —see Beams, wooden. 
Woods of the U. S., list and description 
of most important, 267 
Wrought iron : 
defined,117 

methods of manufacture, 117 
the puddling process, 117 
oxidation in puddling, 119 
details of the puddling process, 
120 

production of muck-bars, 122 
piling and reheating, 123 
the rolls, 123 

effect of numerous pilings and 
rollings, 123 
finished sections, 124 
imperfections in finished iron, 125 
mechanical properties of, 125 

crystalline fractures, the causes of, 
125 

welding of, 128 

effect of reduction in the rolls on 
the strength, 131 
tensile strength, 482 

across the grain, 482 
as affected by pulling speed, 
484 

compressive strength, 484 
shearing strength, 485 
effect of stressing beyond the elas¬ 
tic limit, 486 
chains, strength of, 489 
magnetic testing of, 703 

"\Tellow poplar trees of the U. S., 300 
Yew of the U. S., 279 

i^inc, general properties of, 172 







































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Furman’s Practical Assaying.8vo, 

Kunhardt’s Ore Dressing.8vo, 

* Mitchell’s Practical Assaying, (Crookes.).8vo, 

O’Driscoll’s Treatment of Gold Ores.8vo, 

Ricketts and Miller’s Notes on Assaying.8vo, 

Thurston’s Alloys, Brasses, and Bronzes.8vo, 

Wilson’s Cyanide Processes.12mo, 

“ The Chlorination Process.12mo, 

ASTRONOMY. 


Practical, Theoretical, and Descriptive. 

.4to, 
8vo, 
8vo, 


n so 

4 00 

1 50 
7 50 

2 00 

4 00 

5 00 

1 50 

15 

2 50 
4 00 

50 

1 50 

3 50 

2 00 
2 50 

1 50 

2 00 
1 00 


1 50 
3 00 

1 50 
10 00 

2 00 
3 00 
2 50 
1 50 
1 50 


3 50 

4 00 
2 50 


Craig’s Azimuth. 

Doolittle’s Practical Astronomy 
Gore’s Elements of Geodesy.... 


3 






























Hay ford’s Text-book of Geodetic Astronomy.8vo. 

Mickie and Harlot’s Practical Astronomy.8vo, $3 00 

White’s Theoretical and Descriptive Astronomy.12mo, 2 00 


BOTANY. 

Gardening for Ladies, Etc. 


Baldwin’s Orchids of New England.8vo, 1 50 

Loudon’s Gardening for Ladies. (Downing.).12mo, 1 50 

Thome’s Structural Botany.18mo, 2 25 

We^termaier's General Botany. (Schneider.).8vo, 2 00 


BRIDGES, ROOFS, Etc. 

Cantilever—Draw—Highway—Suspension. 
(See also Engineering, p. 6.) 


Boiler’s Highway Bridges.8vo, 2 00 

* “ The Thames River Bridge.4to, paper, 5 00 

Burr’s Stresses in Bridges.8vo, 3 50 

Orehore’s Mechanics of the Girder.8vo, 5 00 

Dredge’s Thames Bridges. 7 parts, per part, 1 25 

Du Bois’s Stresses in Framed Structures.4to, 10 00 

Foster’s Wooden Trestle Bridges...4to, 5 00 

Greene’s Arches in Wood, etc.8vo, 2 50 

“ Bridge Trusses.8vo, 2 50 

Roof Trusses. 8vo, 1 25 

Howe’s Treatise on Arches.8vo, 4 00 

Johnson’s Modern Framed Structures. 4to, 10 00 

Merriman & Jacoby’s Text-book of Roofs and Bridges. 

Part I., Stresses. 8vo, 2 50 

Merriman & Jacoby’s Text-book of Roofs and Bridges. 

Part II.. Graphic Statics.8vo, 2 50 

Merriman & Jacoby’s Text-book of Roofs and Bridges. 

Part III., Bridge Design.Svo, 2 50 

Merriman & Jacoby’s Text-book of Roofs and Bridges. 

Part IV., Continuous, Draw, Cantilever, Suspension, and 

Arched Bridges.8vo, 2 50 

*Morisou’s The Memphis Bridge.Oblong 4to, 10 00 


4 



























Waddell’s Iron Highway Bridges.8vo, $4 00 

De Pontibus (a Pocket-book for Bridge Engineers). 

Wood's Construction of Bridges and Roofs.8vo, 2 00 

Wright’s Designing of Draw Spans. . . 8vo, 2 50 

CHEMISTRY. 

Qualitative—Quantitative- Organic—Inorganic, Etc. 


Drechsel’s Chemical Reactions. 


Qualitative 


Analysis of Potable Water. (In the press.) 


Poole’s Calorific Power 


12mo, 

1 25 


3 00 

12mo, 

1 50 


1 50 

•) 8vo, 

3 00 

12mo, 

1 50 

12ino, 

1 25 


6 00 


3 00 

>. 16th. 



5 00 

12mo, 

1 50 

12mo, 

1 25 

. .8vo, 

4 00 

12mo, 

1 50 

12mo, 

1 50 

12mo, 

1 00 


3 00 

12mo, 

1 50 


5 00 


2 00 

12mo, 

1 50 

12mo, 

1 00 


2 50 


2 00 

12mo, 

t 00 

12mo, 

1 50 

. 8vo, 

3 00 

(Non- 


rocco, 

75 


5 































Ruddiman’s Incompatibilities in Prescriptions.8vo, $2 00 

Schimpf’s Volumetric Analysis.12mo, 2 50 


Spencer’s Sugar Manufacturer’s Handbook. 12mo, morocco flaps, 2 00 
“ Handbook for Chemists of Beet Sugar House. 

12mo, morocco, 3 00 


Stockbridge’s Rocks and Soils.8vo, 2 50 

Troilius’s Chemistry of Iron...8vo, 2 00 

Wells’s Inorganic Qualitative Analysis...12mo, 1 50 

Laboratory Guide in Qualitative Chemical Analysis, 8vo, 1 50 

Wiechmann’s Chemical Lecture Notes.12mo, 3 00 

“ Sugar Analysis. 8vo, 2 50 

Wulling’s Inorganic Phar. and Med. Chemistry.12mo, 2 00 


DRAWING. 

Elementary—Geometrical—Topographical. 


Hill’s Shades and Shadows and Perspective.8vo, 2 00 

MacCord’s Descriptive Geometry.8vo, 3 00 

“ Kinematics.8vo, 5 00 

“ Mechanical Drawing.8vo, 4 00 

Mahan’s Industrial Drawing. (Thompson.).2vols.,8vo, 3 50 

Reed’s Topographical Drawing. (II. A.).4to, 5 00 

Reid’s A Course in Mechanical Drawing.8vo. 2 00 

“ Mechanical Drawing and Elementary Machine Design. 

8vo. 

Smith’s Topographical Drawing. (Macmillan.).,..8vo, 2 50’ 

Warren’s Descriptive Geometry.2 vols., 8vo, 3 50 

“ Drafting Instruments.12mo, 1 25 

“ Free-hand Drawing..12mo, 1 00 

“ Higher Linear Perspective .8vo, 3 50 

“ Linear Perspective.12mo, 1 00 

“ Machine Construction. . .2 vols., 8vo, 7 50 

“ Plane Problems. 12mo, 1 25 

“ Primary Geometry.12mo, 75 

Problems and Theorems.8vo, 2 50 

“ Projection Drawing. 12mo, 1 50 

“ Shades and Shadows.8vo, 3 00 

Stereotomy—Stone Cutting...8vo, 2 50 

Whelpley’s Letter Engraving.12mo, 2 00 


6 

































ELECTRICITY AND MAGNETISM. 

Illumination—Batteries—Physics. 

Anthony and Brackett's Text-book of Physics (Magie). .. . 8vo, $4 00 


Barker’s Deep-sea Soundings.8vo, 2 00 

Benjamin’s Voltaic Cell.8vo, 3 00 

“ History of Electricity.8vo 3 00 

Cosmic Law of Thermal Repulsion.ISmo, 75 

Crehore and Squier’s Experiments with a New Polarizing Photo- 

Chronograph.8vo, 3 00 

* Dredge’s Electric Illuminations. . . .2 vols., 4to, half morocco, 25 00 

“ “ “ Vol. II.4to, 7 50 

Gilbert’s De magnete. (Mottelay.).8vo, 2 50 

Holman’s Precision of Measurements.8vo, 2 00 

Michie’s Wave Motion Relating to Sound and Light,.8vo, 4 00 

Morgan’s The Theory of Solutions and its Results.12mo, 1 00 

Niaudet’s Electric Batteries. (Fishback.).12mo, 2 50 

Reagan’s Steam and Electrical Locomotives. .12mo, 2 00 

Thurston’s Stationary Steam Engines for Electric Lighting Pur¬ 
poses.12mo, 1 50 

Tillman’s Heat.8vo, 1 50 

ENGINEERING. 


Civil—Mechanical—Sanitary, Etc. 


(See also Bridges, p. 4 ; Hydraulics, p. 8; Materials of En¬ 
gineering, p. 9 ; Mechanics and Machinery, p. 11 ; Steam Engines 
and Boilers, p. 14.) 


Baker’s Masonry Construction. 8vo, 

“ Surveying Instruments.12mo, 

Black’s U. S. Public Works.4to, 

Brook’s Street Railway Location...12mo, morocco, 

Butts’s Engineer’s Field-book.12mo, morocco, 

Byrne’s Highway Construction.8vo, 

“ Inspection of Materials and Workmanship. 12mo, mor. 

Carpenter’s Experimental Engineering .8vo, 

Church’s Mechanics of Engineering—Solids and Fluids-8vo, 

“ Notes and Examples in Mechanics.8vo, 

Crandall’s Earthwork Tables .8vo, 

“ The Transition Curve.12mo, morocco, 


5 00 
3 00 

5 00 

1 50 

2 50 
7 50 

6 00 
6 00 
2 00 
1 50 
1 50 


7 


























* Dredge’s Penn. Railroad Construction, etc. . . Folio, half mor., 

* Drinker’s Tunnelling.4to, half morocco, 

Eissler’s Explosives—Nitroglycerine and Dynamite.8vo, 

Fowler’s Coffer-dam Process for Piers.,8vo. 

Gerhard’s Sanitary House Inspection.16mo, 

Godwin's Railroad Engineer’s Field-book. 12mo, pocket-bk. form, 

Gore’s Elements of Geodesy. 8vo, 

Howard’s Transition Curve Field-book.12mo, morocco flap, 

Howe's Retaining Walls (New Edition.). : ... .12mo, 

Hudson’s Excavation Tables. Yol. II. 8vo, 

Hutton's Mechanical Engineering of Power Plants.8vo, 

Johnson’s Materials of Construction.8vo, 

“ Stadia Reduction Diagram. .Sheet, 224 X 28£ inches, 

“ Theory and Practice of Surveying.8vo, 

Kent’s Mechanical Engineer’s Pocket-book.12mo, morocco, 

Kiersted’s Sew r age Disposal.12mo, 

Kirkwood’s Lead Pipe for Service Pipe.8vo, 

Mahan’s Civil Engineering. (Wood.).8vo, 

Merriman and Brook's Handbook for Surveyors. . . .12mo, mor., 

Merriman’s Geodetic Surveying.8vo, 

“ Retaining Walls and Masonry Dams.8vo, 

Mosety’s Mechanical Engineering. (Mahan.).8vo, 

Nagle’s Manual for Railroad Engineers.12mo, morocco, 

Patton s Civil Engineering.8vo, 

“ Foundations.8vo, 

Rockwell’s Roads and Pavements in France.12mo, 

Ruffner’s Non-tidal Rivers .8vo, 

Searles’s Field Engineering.12mo, morocco flaps, 

Railroad Spiral.12mo, morocco flaps, 

Siebert and Biggin’s Modern Stone Cutting and Masonry.. ,8vo, 

Smith’s Cable Tramways. .4to, 

Wire Manufacture and Uses. 4to, 

Spalding’s Roads and Pavements.12mo, 

Hydraulic Cement. 12mo, 

Thurston’s Materials of Construction .8vo, 

* Trautwine’s Civil Engineer’s Pocket-book. ..12mo, mor. flaps, 

* “ Cross-section..Sheet, 

* “ Excavations and Embankments.Svo, 

8 


$20 00 
25 00 

4 00 

1 00 
2 50 

2 50 
1 50 
1 25 
1 00 

5 00 

6 00 
50 

4 00 

5 00 
1 25 

1 50 
5 00 

2 00 
2 00 
2 00 
5 00 

3 00 
7 50 
5 00 
1 25 
1 25 
3 00 
1 50 

1 50 

2 50 

3 00 
2 00 
2 00 
5 00 
5 00 

25 

2 00 

































* Trautwiue’s Laying Out Curves.12mo, morocco, $2 50 

Waddell’s De Poutibus (A Pocket-book for Bridge Engineers). 

12mo, morocco, 3 00 

Wait’s Engineering and Architectural Jurisprudence.8vo, 6 00 

Sheep, 6 50 

“ Law of Field Operation in Engineering, etc.8vo. 

Warren’s Stereotomy—Stone Cutting.8vo, 2 50 

Webb s Engineering Instruments.12mo, morocco, 1 00 

Wegmann’s Construction of Masonry Dams.4to, 5 00 

Wellington’s Location of Railways.8vo, 5 00 

Wheeler's Civil Engineering.8vo, 4 00 

Wolff’s Windmill as a Prime Mover.8vo, 3 00 

HYDRAULICS. 

Water-wheels—Windmills—Service Pipe—Drainage, Etc. 

(See also Engineering, p. 6.) 

Bazin’s Experiments upon the Contraction of the Liquid Vein 

(Trautwine).8vo, 2 00 

Bovey’s Treatise on Hydraulics.....8vo, 4 00 

Coffin’s Graphical Solution of Hydraulic Problems..... 12mo, 2 50 

Ferrel’s Treatise on the Winds, Cyclones, and Tornadoes.. .8vo, 4 00 

Fuerte’s Water and Public Health...12mo, 1 50 

Ganguillet&Kutter’sFlow of Water. (Hering&Trautwine.).8vo, 4 00 

Hazen’s Filtration of Public Water Supply.8vo, 2 00 

Herschel’s 115 Experiments . 8vo, 2 00 

Kiersted’s Sewage Disposal.12mo, 1 25 

Kirkwood’s Lead Pipe for Service Pipe.8vo, 1 50 

Mason’s Water Supply.8vo, 5 00 

Merriman’s Treatise on Hydraulics.. ..8vo, 4 00 

Nichols’s Water Supply (Chemical and Sanitary).8vo, 2 50 

Ruffner’s Improvement for Nou-tidal Rivers.8vo, 1 25 

Wegmann’s Water Supply of the City of New York.4to, 10 00 

Weisbach’s Hydraulics. (Du Bois.).8vo, 5 00 

Wilson’s Irrigation Engineering.. 8vo. 4 00 

“ Hydraulic and Placer Mining.12mo, 2 00 

Wolff’s Windmill as a Prime Mover.8vo, 3 00 

Wood’s Theory of Turbines.8vo, 2 50 

MANUFACTURES. 

Aniline—Boilers—Explosives—Iron—Sugar—Watches — 

Woollens, Etc. 

Allen’s Tables for Iron Analysis.8vo, 

Beaumont’s Woollen and Worsted Manufacture.12mo, 1 50 

Bollaud’s Encyclopaedia of Founding Terms.12mo, 3 00 

9 































Bolland’s The Iron Founder.12mo, 2 50 

“ “ “ “ Supplement..12mo, 2 50 

Booth’s Clock and Watch Maker’s Manual.12mo, 2 00 

Bouvier’s Handbook on Oil Painting.12mo, 2 00 

Eissler’s Explosives, Nitroglycerine and Dynamite.8vo, 4 00 

Ford’s Boiler Making for Boiler Makers.;....18mo, 1 00 

Metcalfe’s Cost of Manufactures.8vo, 5 00 

Metcalf’s Steel—A Manual for Steel Users.12mo, $2 00 

Reimaun’s Aniline Colors. (Crookes.).8vo, 2 50 

*Reisig’s Guide to Piece Dyeing.8vo, 25 00 


Spencer’s Sugar Manufacturer’s Handbook... .12mo, mor. flap, 2 00 
“ Handbook for Chemists of Beet Houses. 

12mo, mor. flap, 3 00 


Svedelius’s Handbook for Charcoal Burners.12mo, 1 50 

The Lathe and Its Uses. 8vo, 6 00 

Thurston’s Manual of Steam Boilers. 8vo, 5 00 

Walke’s Lectures on Explosives.8vo, 4 00 

West’s American Foundry Practice. .12mo, 2 50 

Moulder's Text-book. 12mo, 2 50 

Wiechmann’s Sugar Analysis. 8vo, 2 50 

Woodbury’s Fire Protection of Mills.8vo, 2 50 


MATERIALS OF ENGINEERING. 

Strength—Elasticity—Resistance, Etc. 
{See also Engineering, p. 6.) 


Baker’s Masonry Construction.8vo, 5 00 

Beardslee and Kent’s Strength of Wrought Iron..8vo, 1 50 

Bovey’s Strength of Materials.8vo, 7 50 

Burr’s Elasticity and Resistance of Materials.8vo, 5 00 

Byrne’s Highway Construction.8vo, 5 00 

Carpenter’s Testing Machines and Methods of Testing Materials. 

Church’s Mechanics of Engineering—Solids and Fluids.8vo, 6 00 

Du Bois’s Stresses in Framed Structures.4to, 10 00 

Hatfield’s Transverse Strains.8vo, 5 00 

Johnson’s Materials of Construction.8vo, 6 00 

Lanza’s Applied Mechanics.8vo, 7 50 

Merrill’s Stones for Building and Decoration.8vo, 5 00 

Merriman’s Mechanics of Materials. .8vo, 4 00 

“ Strength of Materials.12mo, 1 00 

Patton’s Treatise on Foundations.8vo, 5 00 

Rockwell’s Roads and Pavements in France.12mo, 1 25 

Spalding’s Roads and Pavements.12mo, 2 00 

Thurston's Materials of Construction... 8vo, 5 00 

10 





































Thurston’s Materials of Engineering.3 vols., 8vo, $8 00 

Vol. I., Non-metallic .8vo, 2 00 

Yol. II., Iron and Steel.8vo, 3 50 

Yol. III., Alloys, Brasses, and Bronzes..8vo, 2 50 

Weyrauch’s Strength of Iron and Steel. (Du Bois.).8vo, 1 50 

Wood’s Resistance of Materials.8vo, 2 00 

MATHEMATICS. 

Calculus—Geometry—Trigonometry, Etc. 

Baker’s Elliptic Functions.8vo, 1 50 

Ballard’s Pyramid Problem. 8vo, 1 50 

Barnard'3 Pyramid Problem.8vo, 1 50 

Bass’s Differential Calculus...12mo, 4 00 

Brigg’s Plane Analytical Geometry.12mo, 1 00 

Chapman’s Theory of Equations.12mo, 1 50 

Chessin’s Elements of the Theory of Functions. 

Compton’s Logarithmic Computations.12mo, 1 50 

Craig’s Linear Differential Equations.8vo, 5 00 

Davis’s Introduction to the Logic of Algebra.8vo, 1 50 

Halsted’s Elements of Geometry. t ..8vo, 1 75 

“ Synthetic Geometry.8vo, 1 50 

Johnson’s Curve Tracing.12mo, 1 00 

“ Differential Equations—Ordinary and Partial.8vo, 3 50 

“ Integral Calculus.12mo, 1 50 

“ “ “ Unabridged. 

“ Least Squares.-.12mo, 1 50 

Ludlow’s Logarithmic and Other Tables. (Bass.).8vo, 2 00 

“ Trigonometry with Tables. (Bass.).8vo, 3 00 

Mahan’s Descriptive Geometry (Stone Cutting).8vo, 1 50 

Merriman and Woodward’s Higher Mathematics.8vo, 5 00 

Merriman’s Method of Least Squares.8vo, 2 00 

Parker’s Quadrature of the Circle. 8vo, 2 50 

Rice and Johnson’s Differential and Integral Calculus, 

2 vols. in 1, 12mo, 2 50 

“ Differential Calculus.8vo, 3 00 

“ Abridgment of Differential Calculus.. ..8vo, 150 

Searles’s Elements of Geometry.8vo, 1 50 

Totten’s Metrology.8vo, 2 50 

Warren’s Descriptive Geometry.2 vols., 8vo, 3 50 

“ Drafting Instruments.12mo, 1 25 

“ Free-hand Drawing.12mo, 1 00 

“ Higher Linear Perspective.8vo, 3 50 

“ Linear Perspective.12mo, 1 00 

“ Primary Geometry.12mo, 75 


11 






































Warren’s Plane Problems. 12mo, $1 25 

“ Problems and Theorems.8vo, 2 50 

“ Projection Drawing.12mo, 1 50 

Wood’s Co-ordinate Geometry.8vo, 2 00 

“ Trigonometry.12mo, 1 00 

Woolf’s Descriptive Geometry.Royal 8vo, 3 00 

MECHANICS-MACHINERY. 

Text-books and Phactical Works. 

(See also Engineering, p. 6.) 

Baldwin’s Steam Heating for Buildings.12mo, 2 50 

Benjamin’s Wrinkles and Recipes.12mo, 2 00 

Carpenter’s Testing Machines and Methods of Tesling 

Materials.Svo. 

Chordal’s Letters to Mechanics...12mo, 2 00 

Church’s Mechanics of Engineering.8vo, 6 00 

“ Notes and Examples in Mechanics.8vo, 2 00 

Crehore’s Mechanics of the Girder. 8vo, 5 00 

Cromwell’s Belts and Pulleys. 12mo, 1 50 

“ Toothed Gearing.12mo, 1 50 

Compton’s First Lessons in Metal Working.12mo, 1 50 

Dana’s Elementary Mechanics.12mo, 1 50 

Dingey’s Machinery Pattern Making.,.12mo, 2 00 

Dredge’s Trans. Exhibits Building, World Exposition, 

4to, half morocco, 10 00 

Du Bois’s Mechanics. Yol. I., Kinematics .Svo, 3 50 

44 41 Yol. II.. Statics.8vo, 4 00 

“ “ Yol III., Kinetics..8vo, 3 50 

Fitzgerald’s Boston Machinist.18mo, 1 00 

Flather’s Dynamometers.12mo, 2 00 

“ Rope Driving.12mo, 2 00 

Hall’s Car Lubrication.12mo, 1 00 

Holly’s Saw Filing.18mo, 75 

Johnson’s Theoretical Mechanics. An Elementary Treatise. 

(In the press.) 

Jones Machine Design. Part I., Kinematics..8vo, 1 50 

“ “ Part II., Strength and Proportion of 

Machine Parts. 

Lanza’s Applied Mechanics.8vo, 7 50 

MacCord’s Kinematics.8vo, 5 00 

Merriman’s Mechanics of Materials.Svo, 4 00 

Metcalfe’s Cost of Manufactures.Svo, 5 00 

Michie’s Analytical Mechanics.Svo, 4 00 

Mosely’s Mechanical Engineering. (Mahan.).8vo. 5 00 

12 



































Richards’s Compressed Air. 12 mo $1 50 

Robinson’s Principles o f Median ism. gvo 3 00 

Smith’s Press-working of Metals.g vo ;> qq 

The Lathe and Its Uses. _ _ g vo y qq 

Thurston’s Friction and Lost Work..g vo 3 qo 

The Animal as a Machine. 12mo, 1 00 

Warren’s Machine Construction.2 vols., Svo, 7 50 

Weisbach’s Hydraulics and Hydraulic Motors. (Du Bois.).. 8 vo, 5 00 
Mechanics of Engineering. Vol III., Part I., 

Sec. I. (Klein.). 8 vo, 5 00 

Weisbach’s Mechanics of Engineering Vol. III., Part 1., 

Sec. II (Klein.). 8 vo, 5 00 

Weisbach’s Steam Engines. (Du Bois.)... 8 vo, 5 00 

Wood’s Analytical Mechanics. 8 vo, 3 00 

“ Elementary Mechanics.12mo, 1 25 

“ “ Supplement and Key. 1 25 

METALLURGY. 

Iron—Gold—Silver—Alloys, Etc. 

Allen’s Tables for Iron Analysis. 8 vo, 3 00 

Egleston’s Gold and Mercury. 8 vo, I 50 

“ Metallurgy of Silver. 8 vo, 7 50 

* Kerbs Metallurgy—Copper and Iron. 8 vo, 15 00 

* “ “ Steel, Fuel, etc. 8 vo, 15 00 

Kunliardt’s Ore Dressing in Europe.■. 8 vo, 1 50 

Metcalf’s Steel— A Manual for Steel Users..12mo, 2 00 

O’Driscoll’s Treatment of Gold Ores. 8 vo, 2 00 

Thurston’s Iron and Steel.Svo, 3 50 

“ Alloys. 8 vo, 2 50 

Wilson’s Cyanide Processes..12mo, 1 50 

MINERALOGY AND MINING. 

Mine Accidents—Ventilation—Ore Dressing, Etc. 

Barringer’s Minerals of Commercial Value... .oblong morocco, 2 50 

Beard’s Ventilation of Mines.12mo, 2 50 

Boyd’s Resources of South Western Virginia.Svo, 3 00 

“ Map of South Western Virginia.Pocket-book form, 2 00 

Brush and Penfield’s Determinative Mineralogy.Svo, 3 50 

Chester’s Catalogue of Minerals. 8 vo, 1 25 

“ “ “ “ .paper, 50 

“ Dictionary of the Names of Minerals. 8 vo, 3 00 

Dana’s American Localities of Minerals. 8 vo, 1 00 

13 




































Dana’s Descriptive Mineralogy. (E. S.) ... .8vo, half morocco, $12 50 

“ Mineralogy aud Petrography (J.D.).12mo, 2 00 

“ Minerals and How to Study Them. (E. S.).12mo, 1 50 

“ Text-book of Mineralogy. (E. S.).8vo, 3 50 

*Drinker’s Tunnelling, Explosives, Compounds, aud Rock Drills. 

4to, half morocco, 25 00 

Egleston’s Catalogue of Minerals and Synonyms.8vo, 2 50 

Eissler’s Explosives—Nitroglycerine and Dynamite.8vo, 4 00 

Goodyear’s Coal Mines of the Western Coast.12mo, 2 50 

Hussak’s Rock forming Minerals. (Smith.).8vo, 2 00 

Ihlseng’s Manual of Mining. . .. . .8vo, 4 00 

Kuuhardt’s Ore Dressing in Europe.8vo, 1 50 

O’Driscoll’s Treatment of Gold Ores .8vo, 2 00 

Roseubusch’s Microscopical Physiography of Minerals aud 

Rocks (Iddings ).8vo. 5 00 

Sawyer’s Accidents in Mines...8vo, 7 00 

Stockbridge’s Rocks and Soils., ...8vo. 2 50 

Walke’s Lectures on Explosives.8vo, 4 00 

Williams’s Lithology...8vo, 3 00 

Wilson’s Mine Ventilation.l6mo, 1 25 

“ Hydraulic aud Placer Mining.12mo. 

STEAM AND ELECTRICAL ENGINES, BOILERS, Etc. 

Stationary—Marine—Locomotive—Gas Engines, Etc. 

(See also Engineering, p. 6.) 

Baldwin’s Steam Heating for Buildings.12mo, 2 50 

Clerk’s Gas Engine. ...12mo. 4 00 

Ford’s Boiler Making for Boiler Makers.18mo, 1 00 

Hemenway’s Indicator Practice.12mo. 2 00 

Hoadley’s Warm-blast Furnace.8vo, 1 50 

Kneass’s Practice and Theory of the Injector.8vo, 1 50 

MacCord’s Slide Valve.8vo, 2 00 

* Maw’s Marine Engines.Folio, half morocco, 18 00 

Meyer’s Modem Locomotive Construction.4to, 10 00 

Peabody and Miller’s Steam Boilers.8vo, 4 00 

Peabody’s Tables of Saturated Steam.8vo, 1 00 

Thermodynamics of the Steam Engine. 8vo, 5 00 

“ Valve Gears for the Steam Engine.8vo, 2 50 

Pray’s Twenty Years with the Indicator.Royal 8vo, 2 50 

Pupin and Osterberg’s Thermodynamics.12mo, 1 25 

Reagan’s Steam and Electrical Locomotives.12mo, 2 00 

Rbntgen’s Thermodynamics. (Du Bois.).8vo, 5 00 

Sinclair’s Locomotive Running.12mo, 2 00 

Thurston’s Boiler Explosion.12mo, 1 50 


14 






































Thurston’s Engine and Boiler Trials. 8 vo, $5 00 

Manual of the Steam Eugine. Part I., Structure 

and Theory. 8 vo, 7 50 

Manual of the Steam Engine. Part IL, Design, 

Construction, and Operation. 8 vo, 7 50 

2 parts, 12 00 

Philosophy of the Steam Engine.12mo, 75 

“ Reflection on the Motive Power of Heat. (Carnot.) 

12mo, 1 50 

Stationary Steam Engines.12mo, 1 50 

Steam-boiler Construction and Operation. 8 vo, 5 00 

Spangler’s Valve Gears. 8 vo, 2 50 

Trowbridge’s Stationary Steam Engines.4to, boards, 2 50 

Weisbach’s Steam Eugine. (Du Bois.). 8 vo, 5 00 

Wliitham’s Constructive Steam Engineering. 8 vo, 10 00 

Steam-engine Design. 8 vo, 5 00 

Wilson’s Steam Boilers. (Flather.).12mo, 2 50 

Wood’s Thermodynamics, Heat Motors, etc. 8 vo, 4 00 


TABLES, WEIGHTS, AND MEASURES. 

For Actuaries, Chemists, Engineers, Mechanics—Metric 


Tables, Etc. 

Adriance’s Laboratory Calculations.12mo, 1 25 

Allen’s Tables for Iron Analysis. 8 vo, 3 00 

Bixby’s Graphical Computing Tables.Sheet, 25 

Compton’s Logarithms. 12 mo, 1 50 

Crandall’s Railway and Earthwork Tables. 8 vo, 1 50 

Egleston’s Weights and Measures.18mo, 75 

Fisher’s Table of Cubic Yards. Cardboard, 25 

Hudson’s Excavation Tables. Vol. II. 8 vo, 1 00 

Johnson’s Stadia and Earthwork Tables. 8 vo, 1 25 

Ludlow’s Logarithmic and Other Tables. (Bass.).12mo, 2 00 

Thurston’s Conversion Tables. Svo, 1 00 

Totten’s Metrology. 8 vo, 2 50 


VENTILATION. 


Steam Heating—House Inspection—Mine Ventilation. 


Baldwin’s Steam Heating. 

Beard’s Ventilation of Mines.. 

Carpenter’s Heating and Ventilating of Buildings 

Gerhard’s Sanitary House Inspection. 

Mott’s The Air We Breathe, and Ventilation. 

Reid’s Ventilation of American Dwellings. 

Wilson’s Mine Ventilation... 



2 

50 


2 

50 


3 

00 

Square 16mo, 

1 

00 


1 

00 


1 

50 


1 

25 




15 


































MISCELLANEOUS PUBLIC XTiONS. 



Alcott’s Gems, Sentiment, Language.Gilt edges, 

Bailey’s The New Tale of a Tub.8vo, 

Ballard’s Solution of the Pyramid Problem.8vo, 

Barnard’s The Metrological System of the Great Pyramid. .Svo. 

Davis’s Elements of Law.8vo, 

Emmon’s Geological Guide-book of the Rocky Mountains. .8vo, 

Ferrel’s Treatise on the Winds.Svo, 

Haines’s Addresses Delivered before the Am. Ry. Assn...l2mo. 
Mott’ e Fallacy of the Present Theory of Souud.. Sq. lGmo, 

Perkins’s Cornell University.Oblong 4to, 

Ricketts's History of Rensselaer Polytechnic Institute.8vo, 

Rotherham’s The New Testament Critically Emphasized. 

12mo, 

The Emphasized New Test. A new translation. 

Large Svo, 


Totteu’s An Important Question in Metrology...8vo, 

Whiteliouse’s Lake Mceris...Paper, 

* Wiley’s Yosemite, Alaska, and Yellowstone.4to, 


HEBREW AND CHALDEE TEXT=BOOKS. 

Foil Schools and Theological Seminahies. 

Gesenius’s Hebrew and Chaldee Lexicon to Old Testament. 

(Tregelles.). Small 4to, half morocco, 

Green’s Elementary Hebrew Grammar.12mo, 

Grammar of the Hebrew Language (New Edition).8vo, 

“ Hebrew Chrestomathy. Svo, 

Letteris’s Hebrew Bible (Massoretic Notes in English). 

8vo ; arabesque, 

Luzzato’s Grammar of the Biblical Chaldaic Language and the 
Talmud Babli Idioms. 12mo, 

MEDICAL. 

Bull’s Maternal Management in Health and Disease.12mo, 

Hammarsten’s Physiological Chemistry. (Mandel.).Svo, 

Mott’s Composition, Digestibility, and Nutritive Value of Food. 

Large mounted chart, 

liuddiman’s Incompatibilities in Prescriptions.Svo, 

Steel’s Treatise on the Diseases of the Ox.Svo, 

Treatise on the Diseases of the Dog.Svo, 

Woodhull’s Military Hygiene. 12mo, 

Worcester’s Small Hospitals—Establishment and Maintenance, 
including Atkinson’s Suggestions for Hospital Archi¬ 
tecture.12mo, 


$5 00 
75 
1 50 

1 50 

2 00 

1 50 
4 00 

2 50 
1 00 
1 50 

3 00 

1 50 

2 00 

2 50 
25 

3 00 


5 00 

1 25 
3 00 

2 00 

2 25 
1 50 


1 00 
4 00 

1 25 

2 00 
G 00 
3 50 
1 50 


1 25 


1G 












































